I genuinely don't know. They are smart people, they know the game. They must have figured out that there is an upside for them.

Just speculating here. Maybe they have big customers that communicated to them that they will choose them over the competition if they open more of their software stack. Maybe they are less afraid of being sued because they are the underdog and they believe that the authorities would not be kind to a behemoth suing them, or they believe that the behemoth would not sue them because of the bad press it would generate vs the settlement they would get.

I actually don't know. But I am sure they have good reasons, just like the corps that keep it closed also have good reasons. It is not "good" vs "evil".