BitKeeper is a RevisionControlSystem? like CVS. From what I can gather it does things quite differently.
I believe it's quite different because CVS thinks about "per file" changes, where BitKeeper thinks about "changesets" -- 
PerryLorier
Linus is now using BitKeeper for the kernel sources since sometime around 2.4.13
More information 
here.
4 pages link to BitKeeper:
