Rebol stands for Relative Expression Based Object Language. Rebol's webpage states: "Most software systems have become needlessly complex. We rebel against that complexity, fighting it with the most powerful tool available, language itself."
Rebol has been around since about 1998. Rebol version R2 is free to use and it is available on almost any platform. Rebol version 3, or now Rebol was open sourced on 12-12-2012.
Since 2012 development is going on to create a compiled version of Rebol. Initially it was thought this would lead to a reduce instruction set of the Rebol language, hence the name [[Red]] was chosen. In the meantime the goal has been adjusted upward, and aim is now to become worlds first (and only?) fullstack language.
At the end a short warning. When you get Rebol chances are that you will be spoiled forever.