Dear Vasily,
I guess, If you pay out of your own pocket, you are an enthusiast. if it is sponsored by your employer, you are a professional.
Yes, that surely sounds plausible. But I still wonder if that is really all to it. Could the organizers of the summit please clarify officially? Thanks in advance! I just don't think that guessing and trying to read other people's minds is a good approach here. Other LF events have also the hobbyist category, but they usually explain their motivation for it explicitly. The conditions differ, e.g. sometimes active community involvement is necessary, sometime only a limited number of hobbyist registrations is allowed, etc. To put it bluntly, my situation is a bit more complicated given the fact that my employer is, technically speaking, a competition to seL4 :) Best regards Martin Decky