A Mixed Integer Linear Programming (MILP) solver library
lpsolve-5.5.2.5-3-x86_64
It is a free (see LGPL for the GNU lesser general public license) linear (integer) programming solver based on the revised simplex method and the Branch-and-bound method for the integers.
lp_solve solves pure linear, (mixed) integer/binary, semi-continuous and special ordered sets (SOS) models.