I tried running it as a normal user and it works fine. There are no errors and the performance are similar on both cases.
I (and most Linux users) don't want running executables as the root user because (1) it can possibly be a security threat from the program itself or an undiscovered exploit, (2) it requires typing the user's password and kinda annoying for just running a game, and (3) if a user doesn't have `gksudo` installed (i.e. like Windows' UAC prompt) , they need to pull up a terminal which is annoying above that you also need to do #2. And it's much easier to just double-click the executable file than on a terminal
Great game indeed! Even Linux to Windows multiplayer works!