For any one of their product there is a good opportunity to build an open source alternative or something like it! Can be hard to work around they have the benefit of being able to have negative unit economics on lots of infra products... But people succesfully built tons of alternatives to google analytics and similar.

What they are doing requires both physical and digital infrastructure spread throughout the globe. It's not a cheap task.

Open source for bot protection specifically would be difficult. If I as a bot developer can see the tests you run I can just modify my bot to pass them (either trivially or by brute force).