Both are fixing/improving Rebol 3 whilst also developing the R3-GUI (Saphiron work on Windows version while Atronix ported it to Linux desktop).
Unfortunately the Saphiron development isn't kept public so the repo (https://github.com/saphirion/saphir) isn't up-to-date. Atronix is probably the best place to look at this moment (https://github.com/zsx/r3). The last commit was only 6 days ago.
The main Rebol repo (https://github.com/rebol/rebol) keeps getting blocked due to a lack of stewardship :(
At some point this will be fixed. As a stop gap Rebolsources was created and was used by community to filter changes through to main repo. See https://github.com/rebolsource/r3 & http://rebolsource.net/
There are two other versions maintained by two commercial entities:
* Saphiron - http://development.saphirion.com/
* Atronix Engineering - http://atronixengineering.com/
Both are fixing/improving Rebol 3 whilst also developing the R3-GUI (Saphiron work on Windows version while Atronix ported it to Linux desktop).
Unfortunately the Saphiron development isn't kept public so the repo (https://github.com/saphirion/saphir) isn't up-to-date. Atronix is probably the best place to look at this moment (https://github.com/zsx/r3). The last commit was only 6 days ago.