You can also stay on EthOS and simply DONT pay a licence fee.
(see http://ethosdistro.com/ at bottom, .. you should but you dont need to).

Sure, you are cutted off monitoring site and irc support, but you can use your own skills and this forum.
Also you can upload json stats file somewhere else to make own monitoring panel. But its more works that its already done.
I guess you know that you can get under 10$ per rig at mass licencing.

(well .. suggest to switch to Windows seems like an opposite to original question).