Have a look at BQ Cervantes - an open source e-ink reader. Comes with complete sources (sans DRM related stuff) and is designed to be modified by hackers.
See
http://the-digital-reader.com/2015/0...back-in-stock/
I had a look around and it looks like it is *very* niche and there are very few third-party programs for it or independent developers hacking it and publishing results - if any.