Save you all a click: this is about message layer security eg for instant messages, not MLS the American soccer league nor MLS the real estate listing service much loved by American real estate agents.
on second thought there was also the Mozilla Location Service
and about 15 more things i suppose :p https://en.wikipedia.org/wiki/MLS_(disambiguation)
Had never heard of the MLS soccer league until just now.
This is a tech forum.