I don't know that there is a DRM-free part of the library. I know I didn't get an option to add or opt out of DRM when uploading through DistroKid. All I have for comparison is Draft2Digital for eBook distribution, and it does have a DRM toggle.

Though for Spotify and other streaming sites, I would want a DRM option because I provide a way for people to buy the music DRM-free in any format they want with a reasonable license.