As I understand it, there were some investments involved in the development of Rebol2, so it was not possible to release its code. Instead, Carl started Rebol3 as a rewrite. It was first divided into a closed Core library and an open-sourced Host part. Later, both parts were open-sourced, and Carl left.

Rebol3 was always considered an alpha version. In my fork, I've fixed hundreds of bugs and missing features.

And my motivation? I've been using Rebol since its early days. I used it successfully as a scripting language when producing several games. And since I don't make games anymore, I wanted to give something back to this abandoned language, whenever I have the time.

I was also involved in Red (and still follow its development), but for multiple reasons I decided it was better to work alone on the invisible Rebol.