Hey Fabrizio,
I think this is a very case by case issue. For musicianspage.com, I would probably lean towards make it JS based or removing it primarily because most of the profile pages that I saw are pretty empty and I wouldn't want search engines to find a lot of thin content here.
There could be value in this if all users had a more complete profile AND they participated in a lot forum threads - this could help with content discovery (for the threads) and pass link equity to the threads, helping them bring in traffic. If this is your goal, you would need to do a leader board, not just online users, so that you are getting users who have actually answered questions and these users are most likely to invest in their profiles and fill them out well. As it stands now, if you want to keep the online users, I'd probably make it JS based.
Good luck!
-Geoff