Please see the LICENSE or COPYING file in the directories of the individual
library.

In short:
expat: MIT
freetype: FreeType License or GPLv2 or later (see docs/LICENSE.TXT)
harfbuzz: MIT
icu4c: ICU license
libmodplug: Public Domain
libmpg123: LGPLv2.1
libogg: BSD
libpng: zlib
libsndfile: LGPLv2.1
libvorbis: BSD
libwildmidi: LGPLv3
libxmp-lite: MIT
pixman: MIT
SDL2: zlib
SDL2 image: zlib
SDL2 mixer: zlib
speexdsp: BSD
zlib: zlib
