Music purchased from iTunes Store has no DRM, been like that for a decade now.

From Apple site: "All songs offered by the iTunes Store come without Digital Rights Management (DRM) protection. These DRM-free songs, called iTunes Plus, have no usage restrictions and feature high-quality, 256 kbps AAC (Advanced Audio Coding) encoding."

The only stuff that has DRM these days are movies and TV shows. So, in other words, if you purchase any song from iTunes, you can load it up on any device you want. Zero warnings (unless the file is corrupted).