Does a good list of open-content RPGs exist?

Question

I'm looking for open RPGs to play with my group. By "open-content" I mean games that are licensed similar to open-source software—everyone is allowed to get and modify the game and release the result.

The background is that I don't want to rely too much on a system that might die if its creator drops it for whatever reason. If a game is open-content, I and any community that is interested in it can work on it to keep it alive, at least as long as the campaign runs.

So I would appreciate any listing of such games to pick some from for playing.

Answer 1

The Year of Living Free wiki is stuffed with great games using various licenses.

Answer 2

RPG.net has a Wiki entry for open content games here

imPresa Express is missing from that list, link here

Answer 3

John Kim’s various lists are fairly comprehensive. He has one for open gaming.

Answer 4

There is a list of open-content games at Wikipedia. It's not a complete list, but there are enough systems there to keep one group busy for several years.