Requirements: Python 2.7, FFMPEG (Mac and Windows binaries are included in the archive)

Just launch avjoiner.py using Python 2.7.
Open a video file and an audio file and press the "Join" button.
There is currently no way specify the output filename, it will take the name of the input video.
For example, if you're processing "in.mp4" the output will be called "in_joined.mov"