Important distinction: If you’re pursuing unpaid creative endeavors for your own personal enrichment then it’s a hobby (even if you share that hobby with the world). If you’re doing it for someone else (especially for a commercial interest) then it’s working for free.
“I’m playing my guitar in the park because I like to” is a whole different situation than “I’m recording a commercial jingle for the exposure.” Same goes for open-source software: if you’re contributing to the next build of GIMP because you think it’s an interesting side project then that’s fine, but if Adobe asks you to help them create the next version of Photoshop then you shouldn’t take them up on it unless they’re willing to pay.
