Is there any chance of Forest Color getting support open to more renderers soon or does it have to have a lot of custom work done for each?
I'm afraid it will not be possible in the short term. Most of renderers are not compatible with Max texture maps (as Forest Color), and use their own implementation for textures.
Futhermore, they don't offer a SDK which we can use to port Forest Color to their platform. This is even worse with GPU renderers, because GPU code is completely different from CPU.
The only solution would be that we give them the source code of Forest Color, and they write the implementation. But the code has many dependences of other parts of Forest, data structures which are only available from CPU, etc.... not a viable solution really.