The Open Rails program code is published under the protection of the GPL, which is a license devised by the Free Software Foundation which claims it is "the world's most popular free software license".
Sometimes known as "copyleft" in contrast to conventional "copyright", the GPL prevents software which is published without restriction from being re-published with restrictions added. Where "copyright" takes away users' rights, "copyleft" guarantees users' rights.
Open Rails makes use of free software components and tools provided under the GPL and we are grateful to the teams who have made these available for the public good. Such components include:
The GPL is expressly designed to protect program code. For our documents, we use the Creative Commons license "Attribution-ShareAlike CC BY-SA" which lets others remix, tweak, and build upon our work even for commercial purposes, as long as they credit us and license their new creations under the identical terms.
Open Rails adopted the GPL in May 2013 after first securing permission from all the project's contributors. The previous license prevented anyone from taking the code and then distributing a modified version of Open Rails. The aim was to protect the project against splitting into competing versions (known as "forking") which would dilute the effort.
Under this license, Open Rails was not legally open source; but now that the Open Rails project has gained some recognition, we can embrace the free software philosophy and perhaps benefit from forking.