Most files in FFmpeg are under the GNU Lesser General Public License version 2.1
or later (LGPL v2.1+). Read the file COPYING.LGPL for details. Some other files
have a MIT/X11/BSD-style license. 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.GPL 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
- some x86 optimizations in libswscale
- optional x86 optimizations in the files
  libavcodec/x86/h264_deblock_sse2.asm
  libavcodec/x86/h264_idct_sse2.asm
  libavcodec/x86/idct_mmx.c
- the AC-3 decoder in libavcodec/ac3dec.c
- the X11 grabber in libavdevice/x11grab.c

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 nonfree external libraries libamrnb, libamrwb and libfaac can be hooked up
in FFmpeg. You need to pass --enable-nonfree to configure to enable them. Employ
this option with care as FFmpeg then becomes nonfree and unredistributable.
Note that libfaac claims to be LGPL, but is not.

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.