the DRM applied in the shop is not the point, since it is a post-production aspect
the point is they
call it epub altough:
- they reject standard conform i.e. valid epub files when submitted
- they allow $_stuff inside their files (be it code or content) which is NOT supposed or expected to work in an epub file, as defined by said standard.
the point is: whatever datafiles are being used for iBooks, they are no epubs, thus there is neither reason nor justification in calling them this way.