The chat command /mods shows all mods of the server.
but if you add this mod them the players would need a priv called mods.
if they dont have this priv (mods) than they cant see the installed mods
after all they can go to servers.minetest.net to see the installed mods (still working on that)
This is a test mod
Dowload Zip: https://github.com/ManElevation/modspriv
Enjoy ;)