I know you love the word FREE, but this implies there's no need to buy / own the game.
The playing online is "free, forever", as in, cncnet won't suddenly start asking money for it
Though I guess we can't actually guarantee the "forever" part in terms of keeping the service running, technically. Forever is a long time
(though IIRC the server side stuff is freely available, so, yeah.)
If the servers ever go down for some reason they will get back up sooner or later. You cannot kill the Messiah.