SoX source code is distributed under two main licenses. The two
licenses are in the files LICENSE.GPL and LICENSE.LGPL.

sox.c, and thus SoX-the user application, is distributed under the
GPL, while the files that make up libsox are licensed under the less
restrictive LGPL.

Note that some of the external packages that can be linked into libsox
are GPLed and/or may have licensing problems, so they can be disabled
at configure time with the relevant--with-* options. If libsox is built
with such libraries, it must be distributed under the GPL.
