This website (including the wiki) are licensed under version 4.0 or later of the Creative Commons Attribution-ShareAlike International Public License (CC-BY-SA v4.0+), except where noted otherwise.
The COPYING file in the Pacemaker source code repository is the definitive source for licensing information of files provided in that repository. Pacemaker Development in the Pacemaker documentation set also lists licensing information in its FAQ. This page has some further details to add to that.
Common Licensing Questions
The following has been adapted from http://mercurial.selenic.com/wiki/License and (illustrating how complex the issues can be) can only be reproduced here under the terms of the GPLv2.
What does this mean to me?
If you don't distribute "derived works" of Pacemaker, you can do pretty much whatever you want with it and you can stop reading here.
Can I get a commercial license?
Pacemaker is Free Software. To use it for your commercial purposes, simply download it, install it, and enjoy. If you are interested in commercial support, see Support.
When does the license affect me?
If you do not distribute software that works with Pacemaker, you have no license obligations.
If you distribute software that does not modify, copy, or extend Pacemaker's source code and only calls Pacemaker's command line interface, you have no license obligations.
If you intend to distribute software that includes changes to Pacemaker's source code or directly calls Pacemaker's internals, your work may be considered a 'derived work' according to copyright law, and you will need to license your work under a compatible license. We're not lawyers, but this probably means making the source code available under version 2 (or later) of the GPL.
If in doubt, contact the project and/or someone skilled in such matters. We mostly just want to write good software.
What is a "derived work"?
What constitutes a "derived work" can only be precisely determined in a court of law. But conventional wisdom is that if you're modifying Pacemaker, copying or translating significant portions, adding plug-ins, or otherwise linking against its internal interfaces, odds are you're creating a derived work. Such derived works must themselves be licensed under a compatible license.
Depending on your exact circumstances, you might just want to take the easy way out and publish your "derived work" under the GPLv2+, but a lawyer might be able to suggest some alternatives.