>For some reason, I don't believe that is everything your friends need to spark their interest in the game.
>All you get, is a Steam page where people can download the mirrored game files. We will probably not get any more visibility as Steam is a platform catered to commercial games.

I don't fully agree with that. Sure we will just have a mirror. But it's a mirror where several millions of people [1] are able to install and try the game with one click. And also see when their friends play the game.
During the last two years or so I have tried out several indie games on Steam. And quite some of them had a worse interface for network play and menus than Clonk. And yes, I am talking about entering IPs for direct join without being able to copy&paste (you usually get someone in TeamSpeak to spell the IP out for you - or try to memorize it).
I have seen enough to think that Clonk is actually pretty well developed from a technical point of view. Sure it's not AAA-perfect, but it's pretty damn decent for an indie/OS project.

There is a game with a similar story that comes to my mind right now: CS2D. It started as a one man project and is at least as old as 2002. So all people had plenty of time trying the game out, right?
It got greenlighted recently [2] and the developers have written a blog posting [3] saying that over 400'000 people played the game on Steam in the first month.
Even if just 0.1% of these are going to play the game on a regular basis, it's still a huge number compared to our concurrent player counts.

[1] http://store.steampowered.com/stats/
[2] https://steamcommunity.com/sharedfiles/filedetails/?id=915502461
[3] http://steamcommunity.com/games/666220/announcements/detail/2783653064175614582