The main (IMO sad) reason REBOL sits in a weird half-life position of "not quite dead, but..." is that, while REBOL Core is open, the GUI parts (which are crossplatform, and run on Linux) are still closed source.

It's a bit like .NET Core. Great to base a business on... not so great to tinker around with. Arguably the second (tinkering, learning) comes before the first (using what you've learned to build a business).

Mildly infuriating...