Rogue Leader
Over the last week and a half I've been having a lot of fun playing Endless Sky. It's a cross-platform FOSS game that apparently has been around since late 2015, so I wish I had found it sooner. A search through the forums didn't seem to show anyone else has mentioned it before, so I'm making a note of it here. It's available directly from GitHub, Steam, and also commonly included in Linux distributions (albeit perhaps not kept up-to-date).

It bills itself as inspired by the Escape Velocity series (which I'm not familiar with), but as with any space exploration and trading game it's easy to draw comparisons with our beloved Privateer. The immediate and most obvious difference is that it's 'only' a 2D game. While I think this kind of thing might be fantastic to play in 3D, the simplicity of the mechanics also means it's relatively easy to develop and expand (I believe it started as a one-man project). One aspect where 2D simplicity helps is with the player being able to capture and fly a whole fleet of ships rather than just an individual craft as with Privateers 1 and 2. It might be pretty hard to organise and run a fleet in 3D, although I suppose escort ships could just be programmed as allies that fly with you (with formations like in Freelancer).

There are various factions - to begin with the player is pretty much limited to mostly human space although there is limited alien contact at the boundaries of human territory. I believe there are more alien territories (multiple races/factions) with at least some locked behind story walls (I haven't ventured out that far yet). The Human Republic is analogous to the Terran Confederation and the self-declared Free Worlds are analogous to the Border Worlds, but there is also the self-governing Syndicate corporation that runs a number of systems in association with but separate from the Republic. And of course, there's the ubiquitous threat of pirate attack.

There's no major galactic conflict like the Terran-Kilrathi War going on, but the biggest - and so far, only - story campaign seems to be a civil war between the Free Worlds and Human Republic, similar to the Border Worlds crisis of WC4. Like in Wing Commander, I understand the player has a role in shaping the outcome of that conflict, with reconciliation being at least one of the options.

Ship Upgrades
Unlike the Wing Commander universe, humanity is at the bottom of the technology tree. In Privateer, ship upgrades fit directly into various slots/hard-points on a one-to-one basis. Endless Sky takes a slightly different approach with upgrades (or 'outfits' as it calls them) taking a set amount of tonnage or outfit space. A given ship will have a limit on how much outfit space it can accommodate and within that general space there are also limitations specifically for engines (both thrust and steering) as well as specifically for weapons (guns and missiles). General outfits include engine cooling, shield generators, energy generation and storage (for guns), etc. There's plenty of customisation options, but the outfit space constraint often limits what you can do. Of course, that's the incentive to explore - I understand alien technology is not only more powerful than human tech, but is also more space efficient.

Speaking of exploration, one thing that nearly screwed me over at the start was the financial aspect. The player doesn't just start with basic ship like the Tarsus of Privateer, he/she needs to pay off the loan they took to obtain that starting ship in the first place. If I was to start again from the beginning, I would take the freighter option (other choices are a passenger shuttle and a combat-oriented interceptor) as taking on various shipping jobs is the easiest way to quickly earn money to pay off the loan faster. What I didn't realise early on was that every single jump or take-off from a planet counts as a 'day' and every day you are required to pay a portion of your loan. If you run out of funds you're not immediately penalised, but it does degrade your credit rating and your loan repayment increases. If I took just a little while longer to realise this, I could have wound up in the position where I would not be able to earn enough to cover my ever-increasing loan repayments and have to start over.

Unlike Privateer there are no guilds in Endless Sky, but the guilds really only served as extra mission options in Privateer anyway. General missions are easily accessible from the system map (you need to explore to fill out the map, or alternatively purchase a map of the area in the vicinity of your current system at an outfitter) so you can plan ahead and gather multiple jobs to run simultaneously, maximising earnings. Missions are quite varied too: cargo runs, passenger runs, escorts (can be quick money if you jump out to stay ahead of pirate attacks), bounty hunts, etc. There are also some more special jobs that may have a small story chain attached from visiting the spaceport, although these are randomised. Analogous to the fixers in the bars of Privateer, I suppose.

Daily Expenses
Initially the player is likely to only fly single-pilot craft but as he/she buys or captures bigger craft (or even just fields multiple craft), it becomes necessary to hire crew to support your fleet. This is done automatically, but it needs to balanced against how much money you expect to earn on a trip. For the most part I found this isn't a concern until flying the heaviest of warships that requires a minimum crew of dozens. Every day (jump), a crewman requires 100 credits in wages so in a large fleet this can quickly add up costs for a trip and just like with the initial loan repayment it can limit how large you make your fleet. It's possible to park your ships on a planet if you don't want to take your entire fleet with you (and have the extra expense of unnecessary crew).

Capturing Ships
On crew expenses, it's necessary to carry extra crew members above the minimum if intending to capture ships. Being a law-abiding pilot (thus far) I've only captured pirate ships but it's by far the most cost-effective way to expand your fleet. I paid for my first few ships (up to light freighter level, without selling existing ships) but the price of larger ships makes it rather time-consuming to earn the money by just flying regular jobs. The initial ships cost 350-450k, while anything larger than a light freighter costs millions of credits. But by capturing pirate ships, it can add to your cargo and passenger capacity that allows you to take on higher paying jobs - the money is better spent on upgrades/outfits anyway. Not to mention how satisfying it is to take an attacker's assets for your own.

Normally I prefer games with strong story content, but so far I've just been having fun flying within the bounds of human space - I haven't even flown to alien territory yet. I want to try to complete the Free Worlds story campaign first as I understand that will unlock some things that might help in alien space, though I'm having trouble finding how to initiate it (it's not a fixed location like with Sandoval on New Detroit). In the meantime, however, I've still been having fun flying some of the smaller side-story missions.

Lastly, as with any FOSS project, anyone can contribute to it - bug fixes, new content, etc. I daresay it's one of my favourite FOSS games, perhaps second only to The Battle for Wesnoth (which has a completely opposite story background set in high fantasy). If you haven't given Endless Sky a try, I think the zero price tag and space combat/trading environment is a pretty compelling incentive. (I know commercial games have been promoted here, and they have their place, but I think there's fun to be had in free - not just 'free to play' - games too.)
I found the Hai (and their terrifyingly organised Unfettered brethren), and also learned how to plunder the Korath Raiders... I really should finish the FW campaign before exploring further, even if I have Jump Drives now...

I've seen some alien Author ships flying around but haven't yet visited any non-human worlds beyond the Quarg and the Hai.
Call me short attention spanned... the "wall of text being spoon fed line by line on the bottom" delivery for the quests made them not fun for me. I did capture some korath ships and even that world in the center (spoilers) but the story line is smart, just illegible. :(
I think it's the nature of a small community project. Unlike Wing Commander games where the story takes precedence, I think the exploration and game-play aspects are priority here. If they had the artists, they could have a simple 'talking heads' style dialogue. Or even static portraits. But I don't think that's the priority.

I admit I was also put off by the 'wall of text' at first, but once I understood how the game works I started to enjoy it - it seems the stories are more 'icing on the cake' than the focus.

For me, anyway, I'm still having fun flying here, there, and everywhere. At some point I'll exhaust all the exploration and upgrade options, but the fact that I'm spending weeks on an otherwise free game - and having fun with it - is remarkable.

I'm a programmer, I ended up automating the fun out of games I wrote! :)

I'm suggesting though that story delivery is a real problem that should be tackled in this community project. I just may help out once I get some free time. We're lucky to be WC vets, we know how stories can be delivered with limited resources. Some of us should help. ;)
I don't know if the project is big enough to have defined its desired direction in terms of story-telling, or even who is necessarily 'in charge' of making creative decisions like that. I'd suggest - assuming you were super-keen to get involved with this - is to perhaps demonstrate a proof-of concept and find out who to take this to. Looking at the wiki, the current focus seems more to do with game-play aspects and the textual side of story-telling, though I did notice some consideration for photos/renders for backgrounds during story scenes.

Any sort of imagery can help with story-telling. A picture is worth a thousand words, or so the common adage goes. Conversations in the aforementioned Wesnoth are similarly static text, but they are usually accompanied by a character portrait. Combined with visual backgrounds, I imagine this would go a long way to making the game universe 'come alive'. However, Wesnoth is a much older game - at least 12 years older than Endless Sky, and the artistic quality back then was nowhere near as good as it is now (example from 2004). I suspect - assuming Endless Sky takes a similar approach - they may need a similar length of time to reach the same level of quality contributions.
The aesthetics and gameplay are pretty clearly a direct copy of Escape Velocity Nova. That was one of my favorite games of twenty years ago, and for years I always wondered why nobody ever followed up on it. But then this came out, and I barely played it past the tutorial. Oh well.
As I said, I wasn't familiar with the original Escape Velocity series - looks like it was predominantly on Mac? I also noticed this other EV-inspired project that started in 2007 and is still active today, but doesn't seem quite as popular as even Endless Sky. Haven't tried it, though.

Regardless, I'm still having a lot of fun with ES, though I think I'm approaching the end of content for at least the current stable release.
As I said, I wasn't familiar with the original Escape Velocity series - looks like it was predominantly on Mac? I also noticed this other EV-inspired project that started in 2007 and is still active today, but doesn't seem quite as popular as even Endless Sky. Haven't tried it, though.

Regardless, I'm still having a lot of fun with ES, though I think I'm approaching the end of content for at least the current stable release.
Fun Fact: EV Was written by my brother and it's the first time I was ever paid as an artist (At age 13!) :)