Prior art doesn't prohibit someone from patenting the idea ... I rather suspect not too many patent examiners peek inside source code or the interfaces of indie apps to check for prior art, and if a behemoth company is going to patent someone's prior art, it's not as if they're going to submit evidence that disproves their claim.

In short, even if it is prior art, it might still be patented, and some poor shmoe down the road is going to have to research, find, and successfully enter as evidence the prior art. They might just choose to settle instead.

Not playing can still suck.