We've released the schematics, PCB layout, and other design artifacts for the small amount of custom hardware currently used by PiTrac.  See github, here.

On a related note, if anyone is planning on building their own PiTrac DIY LM, we have a few already-manufactured PCB boards in the Maker-Lab.  The first few people to private-message us here on Hackaday.io have the exciting opportunity to purchase a PiTrac Connector Board for US$1 plus whatever shipping is necessary to get where you exist.