That appears to be accurate. BitKeeper froze out kernel developers in April 2005[0] and Git was started the same month[1]:
> Git development began in April 2005, after many developers of the Linux kernel gave up access to BitKeeper, a proprietary source-control management (SCM) system that they had formerly used to maintain the project. The copyright holder of BitKeeper, Larry McVoy, had withdrawn free use of the product after claiming that Andrew Tridgell had created SourcePuller by reverse engineering the BitKeeper protocols.
But as the BitKeeper article makes clear, the relationship between BitKeeper and OSS had been frosty for a while.
And in an interesting twist, it seems that BitKeeper is now Open Source anyway (or at least I see "Now available as Open Source under the Apache 2.0 License" on their webpage) meaning that this could all have been avoided
Going by the posts in the forums[1], it's more that BitKeeper has effectively ceased operations in terms of selling its system.
People have noted multiple times that its current build system is fairly hostile to packaging on *NIX, but nobody seems to be putting in the work and the time. I'm somewhat curious about BitKeeper, but not enough to make my first goal to go down into its guts (complete with a custom stdio from NetBSD with modifications!) to make it play nicely with my system.
Larry McVoy was know for threatening employees of companies using BK and developers of competing VCSs [1], so I understand why so many people wanted to keep away from it.
> Git development began in April 2005, after many developers of the Linux kernel gave up access to BitKeeper, a proprietary source-control management (SCM) system that they had formerly used to maintain the project. The copyright holder of BitKeeper, Larry McVoy, had withdrawn free use of the product after claiming that Andrew Tridgell had created SourcePuller by reverse engineering the BitKeeper protocols.
But as the BitKeeper article makes clear, the relationship between BitKeeper and OSS had been frosty for a while.
[0] https://en.wikipedia.org/wiki/BitKeeper
[1] https://en.wikipedia.org/wiki/Git#History