I understand Arudino consists of both the software (ide + wiring libraries) and hardware (avr, specific header pinout)..

But I'd like to design my own pcb... with some robot specific features.   I plan to use the new open hardware license, and of course I won't be using the "arduino" brand on anything, but I'm curious what exactly does it take in order for full compatibility?

For example, in the IDE, I would love for my would-be board to be listed.     I realize I'd have to add to the software libraries for people to access the added functionality, but is that even possible, or would I have to branch completely on my own... ala 'Freeduino Epic'?

With so many flavors of official arduino boards out there, I assume they've made it easy for themselves to port the ide/software to new hardware, but can I add support for a non-"Arudino" brand board?