Code can still be published and merge requests can still be handled even if the code isn't under an open source license. As a prime example check out Unreal Engine. One of the most popular game engines that powers many AAA games and cinema today. They are not open source, but they actively take outside contributions on GitHub. Though unlike what the parent comment is saying Epic can afford to pay people to work on the project instead of having all of the work done for free.
They let people contribute by making the source open, which also lets the AI companies use it as training data. The question was how would you take contributions without letting the training happen.
Epic makes you agree to a legal agreement before getting access to the source so you could attempt to restrict the source via contract law. The issue is if it does escape to the public, contract law can't save you and copyright law allows for training on it.
Code can still be published and merge requests can still be handled even if the code isn't under an open source license. As a prime example check out Unreal Engine. One of the most popular game engines that powers many AAA games and cinema today. They are not open source, but they actively take outside contributions on GitHub. Though unlike what the parent comment is saying Epic can afford to pay people to work on the project instead of having all of the work done for free.
They let people contribute by making the source open, which also lets the AI companies use it as training data. The question was how would you take contributions without letting the training happen.
Edit: typo
Epic makes you agree to a legal agreement before getting access to the source so you could attempt to restrict the source via contract law. The issue is if it does escape to the public, contract law can't save you and copyright law allows for training on it.