What's the story with patent/license on fractal tree by tokutek (now percona)? Can you use it for personal use only? Ie. you can't use it at work without a license? What about Bε-trees - are there patent free implementations?
Tokutek licensed the fractal tree under GPLv2 with an explicit patent license to make clear that anyone could use the fractal tree code. I don't know what Percona did after the aquisiton.