In terms of historical interest, it's also worth noting why McVoy restricted and eventually withdrew the BitKeeper license: Andrew Tridgell (of Samba and rsync) had begun reverse-engineering the protocol with the eventual intent of implementing a free client.
The resulting debacle was fairly ridiculous; Linux chastising Andrew Tridgell, continued flamewars about using a closed-source product.
What I find interesting here, though, is just how much hot water McVoy landed in. He gave away free licenses to Linux developers, then when someone in that community started reverse engineering his product with the intent to replace it, he revoked the free license, leading Linus to develop a replacement anyway -- one that has largely consumed the vast majority of BitKeeper's target market.