I think they've been pretty noncommittal.
Spolsky: These questions all sort of come back on one another. So what do you think? StackOverflow, open source?
Atwood: I'm torn, because again StackOverflow is very much a commercial venture. Which I guess you could say about ScrewTurn Wiki as well. ScrewTurn Wiki is also commercial. I mean ultimately he wants to get paid for the work he's doing. And I guess I just don't know enough about the repercussions of it to make that decision. I'm not against it by any means. I mean I'm very much pro - as the caller said, Martin said, I'm very much pro open source. And I think I'm just a little nervous, having taken on this project.
Spolsky: But what if somebody cooler than us took that code, and even took, you know, I think we already talked about Creative Commons-ing some of the contributions. So they take the code that we developed, at great expense I'd like to point out - at least six to eight weeks, if not five to seven - and then took all that code and stuff like that, and made another site somewhere that was a better than Stackoverflow. Or it could be called StackDoubleOverflow. It would all be written in English as a second language. And, uh, it would be extremely popular with, say Eastern Europe for example.
Atwood: Right. So that's forking, right? And I have a blog entry about that as well. So the risk was forking is that--
https://stackoverflow.fogbugz.com/default.asp?W4331
So it might happen, or it might not. It doesn't look like they're dead set either way yet.
Edit: Jeremy found a more recent quote than me. Looks like they're still not committing to anything.