Angus Ainslie writes about an open source project a CHIP Pro TNC:
So I finally have a design of the TNC I’ve been working on that I think is ready for release. Initially this started with me wanting a replacement for my mobilinkd and AP510. With feature creep it has turned into much more.
The current board has a VHF radio module, a CHIP Pro computer module running Linux ( NTC calls it gadget OS ) and a Mikrobus slot. I’m currently using the Mikrobus for a GPS module but there are lots of variants.
See the full post on his blog.