With R2, there were certain shortcommings or errors, that meant, we couldn't finish projects the way, we wanted. I saw R2 as a way to develop cross-platform for the major platforms, Windows, Linux, and OS X. And in a way with very fast development, a short way from idea to product.
For some server-side tasks, R2 was good enough in many ways (approaching perfect), but wanting to do graphics and sound and responsive events, there were obstacles.
The desire for an open-source R2 was there. Then we could fix things ourselves. Not develop new, but fix things to get R2 to work as intended across all platforms.
R3 meant new development, not just a fix of things in R2. But if almost starting over, then it could be from any ground, not only R3. And the world around us changed fast with new mobile platforms. We saw new approaches to solve the problem of 'programming' in efficient and rebolish kind of ways, World, Topaz, Red. I started development of World before Rebol was open source. I don't know if this is the case for Topaz and Red too.
On open source, I see benefit in open source, if things needs to be fixed. I don't always see benefit in open source, when new stuff is being developed. You run into the too many cooks problem. I see huge bloat open source projects all over the place. I am being presented them at university, and I run away in horror. They sucks!
New development should be done by one or very few people, if you want somethings really good out of it. That is my view, and I think, it is true in general. But you can probably find projects, where this is not the case.
I hope, Red succeed. I hope, Topaz succeed (it maybe already did, I haven't followed it). I hope, R3 succeed. I hope, Carl succeed with R4. I will do, what I can to get a success out of the World Programming Language.
There are many old-kind-of-languages out there, and we need new modern next-step future-proof rebolish kind of languages!
Not one such language, but several.