Would BLP concerns even need to apply to a project/subproject that is a straightforward simple message board host? At least in article-space, someone can make an argument that the foundation "endorses" the article or otherwise contributes to a libel. But a message board host should be every bit as free from liability as the US Postal Service for the letters it carries, or the phone company for calls that go through its lines, or for the emails written on Gmail.
But of course, I'm not a lawyer, and would love to know if I know what I'm talking about. :)
I think BLP is more a moral issue than a legal one, the foundation is pretty well protected legally. The moral issues are less important for a site where it's clearly just random people chatting than a world-famous encyclopaedia that's at the top of Google results for practically everything, so I think things are ok.