There is a support forum for the product, and all questions should be posted there. http://www.boonex.com/forums/#topic/Deanos-Facebook-Connect-Support.htm
As for your error. The error says it can't recompile your languages. The error is reported by dolphin, not by my module as dolphin handles the install and recompiling operations during the install process.
There is something wrong with your language system. You should be able to verify this by trying to recompile the languages of any of the other modules that are already intalled.
In any case the issue will need to be fixed before the module can be successfully installed. Other new modules you try to install will likely report the same error.