Looks like REBOL 3 (http://www.rebol.com) was abandoned.

The only implementations left are:

• https://github.com/Oldes/Rebol3
• https://github.com/metaeducation/ren-c
• https://www.red-lang.org/

Some binary can be found at http://rebolsource.net/.

Related to

• REBOL as an intercommunication language
• UI Libraries
• short_rebol_examples.r
• RebCode Virtual Machine Developer Guide
• Virtual Machines
• REBOL parsing
• Why Rebol and Red?
• Implementing Multi-User Data Management Applications with Rebol