Welcome to the Forum! No, you don't need RetroPie, this is a 'Stand Alone' Binary. Just Download, extract (uncompress), add some compatible ROMS into the requisite Folder then run the executable program.
Open a Terminal, Then -
'CD' (change Directory) into the PiFBA Folder and run the Binary (the Cog/Gear Symbol).
Link - http://sourceforge.net/projects/pifba/
For all your Emulation needs on the RPi check out my Emulation on the Raspberry Pi&Pi2 Thread!
Link - viewtopic.php?f=78&t=54357