I apologise for the incomplete description; I accidentally submitted the report before finishing it.
Please may I be granted the authority to edit my reports?

To confirm this report, one must download and then unzip tons of data, which might take a while.

Adapted from the PKGBUILD, lines 14-29 (inclusive), with my observations below each entry:

https://www.artsoft.org/RELEASES/rocksndiamonds/levels/BD2K3-1.0.0.zip
- data with no license

https://www.artsoft.org/RELEASES/rocksndiamonds/levels/Boulder_Dash_Dream-1.0.0.zip
- data with no license

https://www.artsoft.org/RELEASES/rocksndiamonds/levels/Contributions-1.2.0.zip
- data with no license

https://www.artsoft.org/RELEASES/rocksndiamonds/levels/Emerald_Mine_Club-2.1.1.7z
- data with no license
- contains media from a proprietary game

https://www.artsoft.org/RELEASES/rocksndiamonds/levels/RS_MIX_01-needs_rnd_jue.zip
- data with no license

https://www.artsoft.org/RELEASES/rocksndiamonds/levels/RS_MIX_01-standalone.zip
- data with no license
- software with no license in the form of source code

https://www.artsoft.org/RELEASES/rocksndiamonds/levels/Snake_Bite-1.0.0.zip
- data with no license
- software with no license in the form of a zipped .d64 file

https://www.artsoft.org/RELEASES/rocksndiamonds/levels/Sokoban-1.0.0.zip
- data with no license

https://www.artsoft.org/RELEASES/rocksndiamonds/levels/Supaplex-2.0.0.7z
- data with no license

https://www.artsoft.org/RELEASES/rocksndiamonds/levels/Zelda-1.0.0.zip
- data with no license
- potential plagiarism/copyright infringement due to similarity to proprietary Nintendo games

https://www.artsoft.org/RELEASES/rocksndiamonds/levels/ZeldaII-1.0.0.zip
- data with no license
- potential plagiarism/copyright infringement due to similarity to proprietary Nintendo games

https://www.artsoft.org/RELEASES/rocksndiamonds/levels/rnd-contrib-1.0.0.tar.gz
- data with no license
- older version of Contributions-1.2.0

https://artsoft.org/RELEASES/unix/rocksndiamonds/levels/rockslevels-sp-1.0.tar.gz
- data with no license
- older version of Supaplex-2.0.0

https://artsoft.org/RELEASES/unix/rocksndiamonds/levels/rockslevels-dx-1.0.tar.gz
- data with no license
- converted from a proprietary game

https://artsoft.org/RELEASES/unix/rocksndiamonds/levels/rockslevels-emc-1.0.tar.gz
- data with no license
- contains media from a proprietary game
- older version of Emerald_Mine_Club-2.1.1

https://artsoft.org/RELEASES/unix/rocksndiamonds/rnd_jue-3.3.0.0.tar.gz
- a variation of the rnd source tree
- source code appears to be free
- embedded contributions have no license

Due to the sheer amount of lack of care for freedom that must have been present in order to accept the gargantuan amount of nonfree data into this 404.8MB (installed size) project, I suspect rocksndiamonds and rocksndiamonds-data may also have freedom issues.
However, I don't think we should jump to blaming the developers when they simply might not have known about the freedom of published works at the time and might have been more careful had they known.

I think the devs should be contacted and asked whether rocksndiamonds and rocksndiamonds-data are actually free, and whether the rocksndiamonds-contrib data are proprietary or whether the license file was forgotten, which seems likely with the various files which were directly contributed to the project and only have the issue of a missing license.