The existing patent agreements are a contributor agreement, not part of the license. So, they restrict people from contributing, but don't actually provide any

The existing patent agreements are a contributor agreement, not part of the license. So, they restrict people from contributing, but don't actually provide any guaranteed protection for downstream users, as far as I can tell. However, I'm not a lawyer and not involved, was just trying to summarize as well as I could, so I could be wrong.