Git, the most popular DVCS, was created in 2005. Some developers of the Linux kernel started to use a proprietary DVCS called BitKeeper, notably Linux founder Linus Torvalds, although some other kernel developers never used it due to its proprietary nature. The unusual situation whereby Linux kernel development involved the use by some of proprietary software "came to a head" when Andrew Tridgell started to reverse-engineer BitKeeper with the aim of producing an open-source tool which could provide some of the same functionality as the commercial version. BitMover, the company that developed BitKeeper, in response, in 2005 revoked the special free of-charge license it had granted to certain kernel developers.