I've used a few different lightweight forms of DRM that don't interfere with User Experience at all, most of which have been unsuccessful (only delaying the inevitable). But there are a few schemes that can be successfully implemented (and so far moderately unbeaten) with appropriate use cases of the tweak. Message me on twitter (@apocolipse269) or IRC (apocolipse on ircsaurik, freenode, chronic-dev, etc) and I can offer some advise. -Apocolipse