The language used in Remote Buddy's user interface is chosen by OS X on the basis of your System Preferences. You can change your language settings in the OS X System Preferences under "Language & Text" in the tab "Language".
There, you can change the order of the languages preferred by you. If Remote Buddy's user interface uses a language you don't speak, please make sure that all of the languages you do speak are located on top of the list found in System Preferences.
Important: Changes to the OS X language settings only become effective after a restart of an application. Therefore, if you've changed the language settings of OS X, you need to first quit, then relaunch Remote Buddy for the changes to take effect.