LEMON is an open source project. You are free to use it in your commercial or non-commercial applications under very permissive license terms.
The project is maintained by the Egerváry Research Group on Combinatorial Optimization [EGRES] at the Operations Research Department of the Eötvös Loránd University, Budapest, Hungary. LEMON is also a member of the COIN-OR initiative [COIN-OR].
If you are interested in starting to use the library, see the Installation Guide.
If you know what you are looking for, then try to find it under the Modules section.
If you are a user of the old (0.x) series of LEMON, please check out the Migration Guide for the backward incompatibilities.