FFmpeg:

 -------
 

 Most files in FFmpeg are under the GNU Lesser General Public License version 2.1

 or later (LGPL v2.1+). Read the file COPYING.LGPLv2.1 for details. Some other
 files have MIT/X11/BSD-style licenses. In combination the LGPL v2.1+ applies to

 FFmpeg.

 Some optional parts of FFmpeg are licensed under the GNU General Public License

 version 2 or later (GPL v2+). See the file COPYING.GPLv2 for details. None of

 these parts are used by default, you have to explicitly pass --enable-gpl to

 configure to activate them. In this case, FFmpeg's license changes to GPL v2+.

 Specifically, the GPL parts of FFmpeg are

 
 - libpostproc
 - optional x86 optimizations in the files
   libavcodec/x86/idct_mmx.c
 - the X11 grabber in libavdevice/x11grab.c
 

 There are a handful of files under other licensing terms, namely:
 
 * The files libavcodec/jfdctfst.c, libavcodec/jfdctint.c, libavcodec/jrevdct.c
   are taken from libjpeg, see the top of the files for licensing details.
 

 Should you, for whatever reason, prefer to use version 3 of the (L)GPL, then
 the configure parameter --enable-version3 will activate this licensing option
 for you. Read the file COPYING.LGPLv3 or, if you have enabled GPL parts,
 COPYING.GPLv3 to learn the exact legal terms that apply in this case.
 

 
 external libraries:
 -------------------
 

 Some external libraries, e.g. libx264, are under GPL and can be used in

 conjunction with FFmpeg. They require --enable-gpl to be passed to configure

 as well.
 

 The OpenCORE external libraries are under the Apache License 2.0. That license
 is incompatible with the LGPL v2.1 and the GPL v2, but not with version 3 of

 those licenses. So to combine the OpenCORE libraries with FFmpeg, the license

 version needs to be upgraded by passing --enable-version3 to configure.
 

 The nonfree external libraries libfaac and libaacplus can be hooked up in FFmpeg.
 You need to pass --enable-nonfree to configure to enable it. Employ this option
 with care as FFmpeg then becomes nonfree and unredistributable.