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# What are the licensing terms? Most of the tools are covered by the GNU GPL, some are public domain, and others have a X11 style copyright. To cover the GNU GPL requirements, the basic rule is if you give out any binaries, you must also make the source available. For the full details, be sure to read the text of the GNU General Public License (GPL). The Cygwin API library found in the winsup subdirectory of the source code is also covered by the GNU GPL (with exceptions; see below). By default, all executables link against this library (and in the process include GPL'd Cygwin glue code). This means that unless you modify the tools so that compiled executables do not make use of the Cygwin library, your compiled programs will also have to be free software distributed under the GPL with source code available to all. ## Cygwin API Licensing Terms This is a copy of CYGWIN_LICENSE from the cygwin sources `This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License (GPL) as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. *** NOTE *** In accordance with section 10 of the GPL, Red Hat permits programs whose sources are distributed under a license that complies with the Open Source definition to be linked with libcygwin.a without libcygwin.a itself causing the resulting program to be covered by the GNU GPL. This means that you can port an Open Source(tm) application to cygwin, and distribute that executable as if it didn't include a copy of libcygwin.a linked into it. Note that this does not apply to the cygwin DLL itself. If you distribute a (possibly modified) version of the DLL you must adhere to the terms of the GPL, i.e. you must provide sources for the cygwin DLL. See http://www.opensource.org/docs/definition_plain.html for the precise Open Source Definition referenced above. Red Hat sells a special Cygwin License for customers who are unable to provide their application in open source code form. For more information, please see: http://www.redhat.com/software/tools/cygwin/, or call 866-2REDHAT ext. 3007`