-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.
+The libcdio, libx264, libxavs and libxvid libraries are under GPL. When
+combining them with FFmpeg, FFmpeg needs to be licensed as GPL as well by
+passing --enable-gpl to configure.
+
+The OpenCORE and VisualOn 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 these libraries with FFmpeg, the
+license version needs to be upgraded by passing --enable-version3 to configure.
+
+incompatible libraries
+----------------------
+
+The Fraunhofer AAC library, FAAC and aacplus are under licenses which
+are incompatible with the GPLv2 and v3. We do not know for certain if their
+licenses are compatible with the LGPL.
+If you wish to enable these libraries, pass --enable-nonfree to configure.
+But note that if you enable any of these libraries the resulting binary will
+be under a complex license mix that is more restrictive than the LGPL and that
+may result in additional obligations. It is possible that these
+restrictions cause the resulting binary to be unredistributeable.