In this case, it looks like Plane is not requiring copyright transfers. So that cuts off the practicality of them ever re-licensing their software (commercially or otherwise). That's a good thing as it means it is indeed not likely the license will ever change. The bad thing is that it would be hard to build a company around this project. The AGPLv3 is just very strict about having to open source any and all bundled features and imposes a lot of restrictions and requirements.