If a game no longer requires DirectX, then it would seem to be an easier task to port it to many operating systems. I don't think this is what is holding back

If a game no longer requires DirectX, then it would seem to be an easier task to port it to many operating systems. I don't think this is what is holding back Linux games. Many game companies already design their games to not rely on DirectX -- none of the games on the PS3, Wii, Mac, or various portables require DirectX. But they will only port to platforms where they think they can make money. Linux's low gamer population doesn't help, nor does the "everything's free" user expectation.