Rebol is a great language that I've been using for years and still am using now. It was unfortunate it wasn't open sourced soon, but in 2012, we finally saw Apache-licensed version. Carl Sassenrath (also author of AmigaOS) the disappeared from the Rebol development (he's now working on Roku) but the community took over the bug-fixing and development and the language still lives on. For the latest "community" version of Rebol, have a look at [1].
There is also Red language [2] that is heavily inspired by Rebol, but is not only interpreted and can be compiled also.
Also, there's an ongoing development effort on "Red" programming language [1a][1b][1c], originally attempted as a +/- open-source clone of REBOL (given that original REBOL had a proprietary license, and after version 2 was stuck in development hell for many years).
Since then, REBOL in a kinda "pre-3" version was (after long nagging by the community, and arguably to everybody's surprise), released under Apache license circa 2012 [2]; though IIUC, in a kinda "unfinished" state, although I'm not really sure to what extent. Still, the Red language development goes on, I believe in part because of somewhat different philosophies and goals.
Back to the language(s) themselves, the REBOL & Red family is very interesting and I think perspective-widening -- which also means it requires some effort to understand well, it's not your typical "Algol in new clothes". What sounds most interesting to me is that it seems to be kinda "dialect-oriented" -- meaning that to use it idiomatically, you should get used to writing tiny parsers (with provided toolbox) for small ad-hoc DSLs. That sounds very nice and interesting, but I unfortunately have one issue with learning that -- that I can't really find good learning resources for that (neither for REBOL nor for Red). Even the official REBOL docs/"manual" seem to be too much "example-oriented" for me; I heavily miss some good "specification"/exhaustive manual, which would show me what are the limits, how does the full BNF look like, etc. In other (old) news, notably, REBOL is cited as an important influence for JSON [2][3].
First time I learnt about REBOL I was in that moment where you struggle trying to understand what to learn as an all around language and why not to learn something like this.
If you are in this same situation right now, I advice you to let go. Point is, despite how good it can be, REBOL has never really taken off so far. It won't take you far. I am still hoping to see it grow up though but I don't have the motivation and resources to help it to that cause; but if you do, then maybe you could take a look at it.
I have also come to make a comment about Red-lang, the mostly compatible spiritual descendent. The next release will have a win32 gui component (followed by other platforms, including Android).
There is a lot of activity on the Gitter room (https://gitter.im/red/red), and updated docs are comimg soon.
It helps keep the fun in computing, and I am very excited by Red.
There is also Red language [2] that is heavily inspired by Rebol, but is not only interpreted and can be compiled also.
[1] https://github.com/metaeducation/ren-c
[2] http://www.red-lang.org