Earlier quoted context omitted.
There isn’t any DRM protected music in the iTunes Store, either. This is only about the previews.
So if I purchase some songs from this store (e.g. someone gives me iTunes credit as a gift) I can still play them without iTunes? I don't need iTunes installed anywhere?
iTunes does embed your Apple ID (you need to sign up and get one to redeem your gift card, though you do not need to enter any credit card info or the like) and purchase date as well as time as metadata in the file, but that information is easily removed. There are no watermarks.