Forking the home screen doesn't matter that much, the basic APIs are
sound. HTC might choose to keep it as a proprietary advantage rather
than donate upstream, which will benefit them but won't significantly
hurt Android as a project.
Forking the platform (a la Linux) is a lot more problematic. Only time
will tell if the new Hero ROMs differ platform-wise. HTC claim perfect
compatibility but as far as I can tell existing notification icons
won't be compatible with their new black notification bar, so who
knows how serious they are about compatibility.
