I know, but why? Due to their size, they must have one of the best legal department in the world. Also, their core business is search, and data processing in g

I know, but why? Due to their size, they must have one of the best legal department in the world. Also, their core business is search, and data processing in general. They have the means of using such software and doing what it takes to comply with the licence without putting themselves in trouble. My guess is simply that they don't want to. They prefer to rewrite it, which will allow them to monetize their tools as proprietary software later. They are already overstaffed with some of the best developers, they can rewrite stuff, and they don't really need help from the open source community, that's why they don't release under copyleft themselves.