I've developed the hardware prototypes and the original firmware (1.0) for my Master's Thesis. The thesis text may be used as a manual for this firmware version.
Pre-compiled firmware images are stored in the GEX binaries repository.
GEX is open-source, all its repositories can be found at git.ondrovo.com/gex. Important firmware repositories:
The protocol is described in the GEX Thesis, which should be enough to port it to any language. Two libraries were developed as a proof of concept:
The GEX hardware is open source, too. The PCBs are drawn in Altium, but the respository includes gerber files and PDFs to make it more accessible.