Wikipedia defines royalties as "usage-based payments made by one party (the "licensee") and another (the "licensor") for ongoing use of an asset, sometimes an intellectual property.". While wikipedia is not authoritive that matchs my own understanding of royalties. By their very nature royalty payments are on going.

Thus Redhat is not paying royalties to FireStar (present tense) they have paid (past tense) money to them as a royalty-buy-out (meaning neither they, nor any downstream user, must pay royalties).

This does not, in any sense whatsoever, contradict the position that royalty encumbered standards are incompatible with the GNU GPL.

Devices based on V-USB (software only USB implementation for AVR microcontrollers) are probably worth a look because designs you can copy are so numerous.

This is one of the most versatile. I doesn't support the Apple IIc yet but the BBC joysticks had a similar capability so the only difference is likely to be in the adapter lead:

http://denki.world3.net/retro_v2.html

Perhaps you don't want to make your own circuit board. If so, I had a quick look at the retro's schematic and reckon you should be able to get the retro firmware running on an off the shelf board such as the one adafruit sell.

http://www.adafruit.com/index.php?main_page=product_info&cPath=16&products_id=174

I've got one of these and its a great little board. I built a temperature logger using one and I got it running (hardware and software) in about four hours. That said I did spend another three building the programmer!

Finally there a gallery of lots of HID devices made using cheap AVR controllers:

http://www.obdev.at/products/vusb/prjhid.html