Unfortunate thing about U++ in this respect is that it agressively uses C++ features - and many of them are not available in other languages (destructors, operator overloading, strong typing, templates). That makes other language bindings possible, but you would loose much of effectivity that way. It would be similar problem as makeing language bindings to boost or STL
As for U++ not being used by Linux distro, that would in fact mean creating new desktop environment. While that is certainly interesting project and U++ is likely to shine in such thing (think e.g. about booting your desktop in 3 seconds , it is unlikely to happen at the moment. The right thing now is Chameleon technology, which will make U++ seamlessly visually integrate with both mainstream toolkits (Gnome and Qt).