The MiniMins app is totally free.
The site has a plugin in order to redirect people on the iphone and android to the app store in order to download the MiniMins application to make it easier to view the site. Particularly if your browsing on a mobile network.
I just had a check and yes it appears it is being directed towards the premium forum runner application.
I have disabled the recommendation to download the app till this is resolved.
To get the MiniMins app, go to the app store and search for "MiniMins".
Pierce