The NumWorks graphing calculator

I think Free Software people are rightly wary of non-free software. So long as this system is CC-BY-NC-ND they can decide tomorrow that actually they'd rather you upgrade to their new device and cease all support for the old one. Any attempt by developers like yourself to keep it going would then be illegal, and it's up to them what they choose to do about that but it's unlikely to be comfortable for you. You might say you're sure the current leadership would never do that to you but (a) that's worth nothing in a court of law and (b) none of us is invulnerable to the effects of being hit by a bus, tomorrow this whole project could be owned by Casio or whatever.

If as the article hints they move to CC-BY-NC that's still not free, but it's a healthier situation in which to be volunteering your efforts because (so long as it remains a hobby) it can keep going without the say-so of the original creators.