It's free software, so anybody may use it and adapt it to her/his needs. Though the better starting point is this:
https://www.mobileread.com/forums/sho...d.php?t=228167
As far as I can see, there is groundwork for developing user apps on that device:
http://sourceforge.net/projects/pocketbook-free/
That said - well, it needs some development skills. To do it myself, I lack the device and the time.