As a network nerd, I'm kind of interested in learning to write atlk/adev devices, but I can't find much information on how to do so aside from the source code for bbraun's Appletalk VPN and the name of a fabled document entitled "Macintosh AppleTalk Connections Programmer's Guide", which I have not been able to track down anywhere except as a part number.
The Appletalk VPN code has been extremely useful in getting an overall understanding of how this works, and I'm thinking I'm ready to start hacking, but I'm not sure what terms the VPN source code is provided under: is it OK to use this as a starting point/basis? Obviously, in the vanishingly unlikely event of me producing anything worthy of use by other people, relevant credit would be given...
Yeah, I heard about that mythical document too when I was trying to write the adev, but was never able to track down a copy. I ended up spending many hours in macsbug and using minivmac's FDisasm for disassembling things.
Feel free to use it as a starting point. Consider it under the 3 clause BSD license.