Kodi features repo of additional plugins. RMS stated (see reference for links) that repos like that should have only free software, otherwise entire software is considered nonfree (http://lists.nongnu.org/archive/html/gnu-linux-libre/2016-04/msg00116.html). Parabola patches Kodi to use their own hosted Kodi repo, see patch: https://git.parabola.nu/abslibre.git/tree/libre/kodi/libre.patch.
We could either use their repo or create our own. But maintaining such repos could be pita.