To those wondering about GoG's current policy. Here is a letter sent last year to to the Red Eclipse team and explains why there hasn't been any more free games and projects added since the initial list containing Warsow.
http://redeclipse.net/forum/viewtopic.php?f=4&t=614#p5385 A lot of good mentions so far I completely forgot about last night, I didn't see the previous thread which has a great list on the first post. There are so many threads on General Discussion Things get totally buried very quickly. There needs to be a sticky. I was originally intending on drawing the line at ongoing open source projects where the assets are totally free. But I may have to rethink that to include non open source as well as you all have put up quite a few great titles that probably deserve to be mentioned. Games like Dwarf Fortress (orbiter isn't FOSS anyway) But I didn't include OpenRA (AFIK you need game data files which are not free.)
@Rampancy Fanmade Marathon Games are already on SBO (got to simplify the list somehow or people would be looking all day)
{EDIT} I forgot westwood released the game game assets for the original C+C and it's affiliates, So yeah that's definitely going on the list.