Being within the bounds of literal and legal correctness and acting like an asshole, it turns out, are not incompatible!

I don't see this as asshole behavior. They're giving away an overwhelming amount for free, which the community or a competitor can build upon at any time. This project being an example.

For those who find the closed capabilities and extensions distasteful there is opportunity to make their own.

I've got several decades of experience with the things Microsoft has given away for free. I consider this to be an (entirely on-brand and consistent) asshole move, part of the same EEE cycle we've been through a dozen times with a dozen product lines. It's enough to keep me off even the open-source rebuild of the product.