iTunes music is now DRM free, but in regards to other data (movies, shows, books, apps, etc) it gets a bit more complex. The 5 "device" limit is actually only relevant to computers. 5 computers can have their iTunes applications linked to an account. Once you get to iOS, any device that is synced with those computers can play that data. You also can log into any number of accounts on an iOS device to redownload/purchase applications etc, however those items will be deleted if you want to sync again with your computer and it is not registered with that Apple ID. And obviously you can deauthorize a computer at any point as well (and are allowed a batch reset once a year iirc).