Obvious problems with the source of this editorial aside, I do think that the overall idea has some merit.
(As so do 61% as by a Phoronix poll:
http://www.phoronix.com/scan.php?page=n ... nhill-Poll :rolleyes: )
I see two issues behind this decline in project contributions or new (somewhat successful) projects started:
1. (more minor) Other games on the main platform of FOSS games (Linux) distract the audience away from FOSS games, but not so much the main creators. But creators are motivated by an audience and outside contributions are more likely (as few and far in between as they usually are) for games that have a larger audience.
2. The main reasons is the Indie boom and apocalypse we are currently experiencing. Before many people were modding games or making FOSS games to get some credibility for a job in the games industry, but a few years ago this changed and everyone started to believe they can make a profitable indie game in their basement. Obviously this isn't true and maybe 1 in 10 released Indie games barely break-even and much more probably failed before their release. More and more people are realizing this right now, but during the boom this drained away a lot of potential FOSS game contributers and now the "indie apocalypse" is leaving a lot of very disillusioned and bitter Indie developers behind (with no financial resources left and very little motivation to do any more work for "nothing").
TL; DR: It comes down to basic human psychology... lure someone with a dream of becoming rich fast and you get some pretty bad outcomes for most of them and their surroundings...
Edit: About retro games and 2D games etc.: Yes there is a tiny niche for some FOSS games there, but it's impossible to compete with nostalgia coupled with the highly polished commercial games of the 1990ties, thus I don't think "retro" gamers have much interest in FOSS games.