Thanks for this update. I was not aware of it.
I searched for the reason why it is not in Soft database and found this link with the appdata load results:
https://github.com/hughsie/createrepo_as_logs/blob/master/f/freedroidrpg.log
https://alt.fedoraproject.org/pub/alt/screenshots/f24/matrix.html

The second link seems to be be better for issue understanding and confirms your finding of the wrong/missing icon file.
Well I think fixing this issue should get Freedroid in Gnome Soft.