When I was in college, I was dating a girl who was taking a philosophy class that was particularly interesting to me. One day we were hanging out before her class and she was telling me about their discussions, and it covered some ideas I really enjoyed discussing. Since I was in computer science, I never got the opportunity to take a lot of humanities like Philosophy and so I mentioned that I wished I could take this class. She had to go to class and just said "you can come with me if you want".

I went with her and just sat down. I took notes, I participated in discussion, and ended up going back for several weeks. I eventually stopped going as they moved onto another chapter. I popped back in a few weeks later and the only thing the teacher said when they saw me come into the lecture hall was "hey it's good to see you again". The prof knew I existed but either didn't realize or didn't care that I wasn't actually on the class roll.

That's fine though, and it's exactly how we would want it to be aka it's for the students but if someone is ernest they can just 'participate' in some thing. That's a positive outcome I can't fathom getting upset by that.

That said, showing up for a class isn't exactly 'an education' either.