I've tried on a MacBook Pro with both Apple's built-in IR receiver and an eHome receiver and could not reproduce this. The system went to sleep after the time specified in System Preferences. There also haven't been any changes in Remote Buddy that could have an effect on sleeping or screen savers in a very long time.

Please be aware that - with default settings - each button press you perform is seen as "activity" by OS X. Just like the press of a key on a keyboard or a button on a mouse or trackpad.

If this is not the behaviour you want, you can turn it off at Remote Buddy > Prefs > General > Advanced.

Please note that, if you're using a built-in Apple IR Receiver and you're not using Remote Buddy's driver, the OS X Apple Remote driver that's used then will most likely always create "activity" and this setting will not have any effect.

Best regards, 
Felix Schwarz