HandBrake is an open-source video transcoder available for Linux, Mac, and Windows, licensed under the GNU General Public License (GPL) Version 2
HandBrake relies on many 3rd party libraries which are built from source when compiling HandBrake. These are downloaded at compile time from handbrake.fr or the 3rd party library websites.
For posterity, this repository has a release which archives all the 3rd party source downloads in the event they are no longer available on handbrake.fr or upstream.