Let's stop the FUD already, okay?
Yes, Apple Music has a DRM component. Yes, it sucks, but it's similar to every other streaming service. No, it does not overwrite the files on your Mac to make all your music DRM-laden. For those Googling in a panic, here's the deal.
Anything you download from Apple Music's streaming catalog is DRM-protected
Just like every other streaming service, Apple adds a DRM (digital rights management) layer to its streaming music collection. This keeps you from getting a subscription, downloading a ton of music in month one, then canceling the subscription. Instead, if you cancel Apple Music, all that streaming music becomes inoperable.
If you want DRM-free versions of that music, you can always buy tracks and albums from iTunes, Google, Amazon, or any other number of retailers.
iCloud Music Library doesn't DRM everything
Just like with the company's iTunes Match service, Apple Music allows you to upload the music you own on your Mac to iCloud; from there, you can stream and download it using your iCloud Music Library to your other devices.
Apple's upload algorithm for Apple Music works in two parts. First, it scans your library for any tracks that also happen to be in Apple Music, and matches those together—so when you download a copy of your song on a different Mac, iPhone, or iPad, you're getting the high-quality 256kbps version from the Apple Music catalog.
Then, any songs it can't match, it uploads directly to iCloud; when you download a copy of those songs on a different device, you're getting the same file you had on your Mac.
So what gets DRM? Any matched track you download to another device. It gets DRM because the file itself is coming directly from the Apple Music catalog, which, as we established above, has DRM on it.
Uploaded tracks that you re-download will never get DRM, because they're not coming from the Apple Music catalog.
If you enable iCloud Music Library on your Mac, those songs will not automatically get replaced with DRM versions
This seems to be where people are getting confused, and I just want to straighten this out right here:
Apple is never going to replace the music you've already downloaded with DRM copies.
Okay? Here's why. Your hard-copy music library on your Mac is yours. Apple may scan it for inclusion in iCloud Music Library on the iCloud server, but they have no control of your hard drive's tracks. So, if you're worried that Apple is magically turning any matched songs in your library to DRM copies, they're not.
iCloud Music Library is not a backup service
That said: Do not upload all your tracks from iTunes to iCloud, then delete the local copy on your Mac. If you do that, you're getting rid of your original, DRM-free copies. And you're leaving yourself without a physical backup of your data, which I never, ever recommend.
Also, this is how disinformation like "iCloud Music Library is DRMing all the music on my Mac!" gets disseminated. Because if you upload all your music to iCloud Music Library, then delete it, then redownload it to your Mac, iCloud is going to assume you're downloading that track onto an auxiliary device, and send you the matched tracks. Which have DRM on them.
This is the only way you can end up with DRM-laden music on your Mac that's technically yours: by deleting your original copies. Don't delete your original copies, and you won't have a problem.
If you don't want DRM on copies of your iTunes music, use iTunes Match (or turn off iCloud Music Library)
Don't like the idea of DRM on your matched songs for auxiliary devices? You've got two options.
Option one: Use iTunes Match
iTunes Match ($25/year) performs essentially the same service as Apple Music, but it matches tracks with the iTunes Store catalog, which is DRM-free. As such, when you redownload a matched track or download it to another device, it's a DRM-free file that can never be taken away.
If you use both Apple Music and iTunes Match, the Store catalog supercedes the Music streaming catalog; you should always be getting DRM-free files if you subscribe to Match. If for some reason you're getting Apple Music files, don't panic: it's a bug. Try logging out and logging back in again, or deleting and redownloading the file.
Option two: Turn off iCloud Music Library on your Mac
Don't want your Mac's files getting scanned? Turn off iCloud Music Library on your Mac. In iTunes, go to Preferences > General > Uncheck iCloud Music Library.
You can still keep iCloud Music Library active on your iPhone, iPad, or iPod touch and add tracks from there if you don't mind not having your Mac's library streaming to your other devices; you can also make a secondary user account on your Mac that has no music and iCloud Music Library enabled so that you can listen to your streaming catalog on OS X. But if you don't want it to scan your files, you don't have to let it.
Still confused about DRM and Apple Music? Let me know in the comments and we'll try and get you a fix.