Moving, copying, deleting files: they are all already implemented and stable. Madshelf reads tags from different formats and does all sorts of other nifty stuff. It is also skinable.
PDF support is on its way - MadPDF is already working (I'm the main dev on that one, too). MadPDF will have panning, zooming, dynamic trimming; it will be a PDF reader/viewer fully adapted to eink readers.
For the DRM stuff, that's not my department. The IRC channel (#openinkpot on OFTC) is a good place to ask questions.
But this is a community project, so join the community to get the specific features you want!
Note: if you want to help develop apps, it is possible to develop on your desktop machine, using EFL (the Enlightenment Foundation Libraries), which means you don't have to necessarily know about cross-compiling and other advanced things.