An important note about BitKeeper: it is not real open-source, and
certainly not GPL compliant. It conflicts with two clauses of the OSI.
1) the license cannot discriminate among various uses of the software,
and 2) the license must respect the users' privacy. The BK license
forces a release of private information with the BK logging servers
that collect source control history logs. As a result of this, the BK
license indirectly discriminates against commercial use.
Now, if you want to use BK, go for it. I use plenty of non open-source
software, sadly, being a Mac user and all. Just don't go using BK
thinking it is open-source or free software.