MusicBrainz houses metadata on demoscene "musicdisks", which are basically freely distributed executable programs (whether as a ZIP file, IMG file, physical media like floppies, etc.) that act as music compilation albums. Such recordings are presented as module/tracker music files (e.g. .MOD, .XM). One such example is Chipdisk #1 by Razor 1911. Outside of this, tracker music can be easily added as recordings and possibly works on MusicBrainz. (e.g. Jayce's "beyond weird iii")

The demoscene have their own communities and databases, which in my opinion should be suitable for the other databases whitelist and maybe some URL relationships.

I think one main issue pertaining to recordings however would be that some of these songs may have been re-released on music stores or streaming for a fee, and it might be ironically seen as piracy. However on the other hand, this may be nulled by the fact it was released for free in the past in the first place.

Pouet is basically the community hub for the demoscene. It houses a user community as well as a database for demoscene productions. Most if not all accounts on Pouet tend to be the official user accounts of the people involved in the productions.

• Production: https://www.pouet.net/prod.php?which=5022
  Closest equivalent to MusicBrainz would be a release.
• Group: https://www.pouet.net/groups.php?which=156 
• User: https://www.pouet.net/user.php?who=1811 
  Might be linkable to artist under "social media"? 

Demozoo is essentially a database like MusicBrainz for the demoscene.

• Production: https://demozoo.org/productions/199179/
• Group: https://demozoo.org/groups/1853/ 
• Artist: https://demozoo.org/sceners/10035/

Some recordings are streamable for free through Demozoo but this isn't always the case. beyond weird iii is, but the individual recordings on The HER Collection are not (example here - rather, they go through YouTube).

AMP ("Amiga Music Preservation") is a database for housing tracker music recordings, mainly in file types intended for the Amiga.

• Artist: https://amp.dascene.net/detail.php?view=2539
• Group: https://amp.dascene.net/newresult.php?request=groupid&search=3369 
• Recording (download): https://amp.dascene.net/downmod.php?index=25017
  Could be added as free download?
• Recording (analysis): https://amp.dascene.net/analyzer2.php?idx=25017
  Sidenote, sometimes the artist will put some notes in the file itself, typically with sample names.

Nectarine is an online radio for tracker music where people can log in and request a song to be played. I'm not sure if this should be added or not, but it can act as another database for demoscene music.

• Artist: https://www.scenestream.net/demovibes/artist/2920/
• Group: https://www.scenestream.net/demovibes/group/42/
• Song: https://www.scenestream.net/demovibes/song/33768/

The MOD Archive is what it says on the tin, an archive for tracker music recordings. It doesn't provide as much metadata as the others, but this would still definitely be useful for recording relationships as they provide a free download and the ability to stream for free, so combined with the above I think it'll be a good addition.

• https://modarchive.org/index.php?request=view_by_moduleid&query=103927