Hmm... yes and no, but mostly no. Certainly, you don't need to have KSaga to be able to download them. But, you won't be able to install them without KSaga installed.
At the same time, the KSaga add-ons can be partially used with the DOS version of WC and WC2. I had done some extensive experiments with this, back in the day what I didn't have KSaga. Keep in mind though, that while I had quite a bit of success persuading the WC2 addons to play nice with the DOS version, the WC1 addons are nasty beasts which cannot be persuaded to work properly.
Therefore, the question of whether they're freeware or not is moot. If you've got KSaga, you're free to download and use them. If you don't... you're still free to download them, but you can't use 'em; their legal status doesn't change that basic fact.