[HansTWN]

With that current DRM mess, different devices support different systems and that are mutually exclusive, content providers are virtually asking customers to un-DRM the files. I would have no problems with DRM if all devices used the same system and you could transfer the files to any new devices (and remove them from the old devices). We have the same nonsense with regional restrictions on DVDs, etc. They are forcing people to work around these. Laws are very different in different countries, the US has the most restrictions. In Germany circumventing DRM for personal use (backup copy, second home, etc) is legal for DVDs, so most probably it is for e-books, too. But generally you have a lot fewer rights with digital copies than with physical copies.

Anyway, if you sell the books with DRM and do not keep copies for yourself nobody will sue you, and no court would convict. Many stipulations in contracts are not actually binding, some rights you cannot just "sign away", even if it says so in the fine print.