All PulseAudio source files are licensed under the GNU Lesser General Public License. (see file LGPL for details) However, the server side links to the GPL-only library 'libsamplerate' which practically downgrades the license of the server part to GPL (see file GPL for details), exercising section 3 of the LGPL. Hence you should treat the client library ('libpulse') of PulseAudio as being LGPL licensed and the server part ('libpulsecore') as being GPL licensed. Since the PulseAudio daemon and the modules link to 'libpulsecore' they are of course also GPL licensed. Andre Adrian's echo cancellation implementation is licensed under a less restrictive license - see src/modules/echo-cancel/adrian-license.txt for details. -- Lennart Poettering, April 20th, 2006.