liblo is an implementation of the Open Sound Control protocol for POSIX systems, started by Steve Harris and now maintained by Stephen Sinclair. It is released under the GNU General Public Licence. This means that it cannot be used in closed-source systems you intend to distribute - if you have a specific requirement for liblo in a close-source system then mail me and I may relicense it on an individual basis.
You can read HTML API documentation online or look at example code. Man pages and PostScript docs can be built from the source tarball using doxygen.