Maybe the fact WebObjects was removed from Snow Leopard Server means they don't depend on it internally as much? It seems like they've been cooling off on Java development and support over the last few years.
I believe that the current WebObjects license (while no longer having a licensing fee) stipulates that it should be run on Apple hardware. Some wags have speculated that it would be OK to run it on an Mac Pro even with Windows 7. I don't believe this is an immediate issue, but one that people doing long term planning should consider. If you want to write/run Java code, have at it. If you want to write something that…
That was when the software price started at 50k (iirc) though. When you're charging that kind of coin, I guess the motivation to support Windows is higher.