These are Steve Baker <sjbaker1@airmail.net>'s portability libraries. They
are licensed under the LGPL.

From the README:

The following libraries are provided:

JS  -- A Joystick interface.
PUI -- A simple GUI built on top of OpenGL.
SG  -- Some Standard Geometry functions (vector and
       matrix math, spheres, boxes, frustra, etc)
SL  -- A Games-oriented Sound Library.
SSG -- A Simple Scene Graph API built on top of OpenGL.

WWW: http://www.woodsoup.org/projs/plib

- Brian Buchanan
brian@CSUA.Berkeley.EDU