X Window System source code is covered by many licenses. All of these licenses have in common the fact that they do not impose significant conditions on the modification or redistribution or either source code or binaries beyond requiring one or more of the following:
Most of these licenses are based on the MIT, X Consortium, or BSD (original and revised) licenses. All of them are consistent with the Open Source Definition, and most are consistent with the Free Software Foundation's Free Software Definition.
Copyright and Licensing information for X, including the reproduction of copyright and/or license notices and attributions required by some of the licenses for binary distributions, can be found in the License Document. If you find any omissions in that document, please contact us with details at firstname.lastname@example.org . While the current licenses are all open source licenses, the X.Org Foundation is attempting, with time, to bring as much as possible of the code's licenses in the distribution into compliance with the Debian Free Software Guidelines.