Avidemux is GPL V2.
It contains other software included as source with the following licenses :
Name    : Secret Rabit Code
URL     : http://www.mega-nerd.com/SRC
License : GPL 

Name : Tinypy
URL: http://www.tinypy.org
License : MIT + PYTHON SOFTWARE FOUNDATION LICENSE VERSION 2 

Name    : ffmpeg
URL     : http://www.ffmpeg.org
License : GPL >=2

Name   : SQLite3
URL    : http://www.sqlite.org
License: Public Domain

Name   : Spidermonky
URL    : https://developer.mozilla.org/en/SpiderMonkey
License: GPLv2

URL    : http://resare.com/libmp4v2
License: LGPL
Name   : liba52
URL    : http://liba52.sf.net
License: GPL

Name    : Mad
URL     : http://www.underbit.com/products/mad
License : GPL

Name   :  TwoLame
URL    :  http://twolame.sf.net
License:  LGPL

