\(\renewcommand{\AA}{\text{Å}}\)

# 1.6. LAMMPS open-source license

## 1.6.1. GPL version of LAMMPS

LAMMPS is an open-source code, available free-of-charge, and distributed under the terms of the GNU Public License Version 2 (GPLv2), which means you can use or modify the code however you wish for your own purposes, but have to adhere to certain rules when redistributing it - specifically in binary form - or are distributing software derived from it or that includes parts of it.

LAMMPS comes with no warranty of any kind.

As each source file states in its header, it is a copyrighted code, and thus not in the public domain. For more information about open-source software and open-source distribution, see www.gnu.org or www.opensource.org. The legal text of the GPL as it applies to LAMMPS is in the LICENSE file included in the LAMMPS distribution.

Here is a more specific summary of what the GPL means for LAMMPS users:

(1) Anyone is free to use, copy, modify, or extend LAMMPS in any way they choose, including for commercial purposes.

(2) If you distribute a modified version of LAMMPS, it must remain open-source, meaning you are required to distribute all of it under the terms of the GPLv2. You should clearly annotate such a modified code as a derivative version of LAMMPS. This is best done by changing the name (example: LIGGGHTS is such a modified and extended version of LAMMPS).

(3) If you release any code that includes or uses LAMMPS source code, then it must also be open-sourced, meaning you distribute it under the terms of the GPLv2. You may write code that interfaces LAMMPS to a differently licensed library. In that case the code that provides the interface must be licensed GPLv2, but not necessarily that library unless you are distributing binaries that require the library to run.

(4) If you give LAMMPS files to someone else, the GPLv2 LICENSE file and source file headers (including the copyright and GPLv2 notices) should remain part of the code.

## 1.6.2. LGPL version of LAMMPS

We occasionally make stable LAMMPS releases available under the GNU Lesser Public License v2.1. This is on request only and with non-LGPL compliant files removed. This allows uses linking non-GPL compatible software with the (otherwise unmodified) LAMMPS library or loading it dynamically at runtime. Any modifications to the LAMMPS code however, even with the LGPL licensed version, must still be made available under the same open source terms as LAMMPS itself.