You need to apply once a year and you need to be a maintainer of an active oss project for the oss license. From my experience they're very lenient in regards to what they consider active, but I don't think I'd jump trough the hoops if I didn't start using Rider with the student license.
Free for non-commercial offers a easy way to get people to use it and hopefully advocate for it at their jobs.
I did jump through the hoops every year and it's mostly fine, a 20m form filling exercise. I only had to explain one time that my project was still ongoing despite having a lot of seemingly automated commits.
Free for non-commercial offers a easy way to get people to use it and hopefully advocate for it at their jobs.