Oh, you mean retail expansion packs? Aside from the initial three versions of the main game itself, I don't think any were released. Origin might have had some small ones available from its bbs or via mail.
Only the main game for Apple 2, Commodore 64 and PC were released, unless the expansions had a different name. The term "modules" is kind of weird. If that's actually what they're called, then they indeed were probably only available directly from Origin.
None were released. Origin sent out a letter saying something to the effect that it was no longer worthwhile working on (shrinking market.) Not their exact words. I have the letter around here somewhere.