The Keystone Application at least partially implements several open standards published by the World Wide Web Consortium (W3C). The W3C Patent Policy Working Group states that (quote):
"The W3C Patent Policy governs the handling of patents in the process of producing Web standards. The goal of this policy is to assure that Recommendations produced under this policy can be implemented on a Royalty-Free (RF) basis."
The official W3C Patent Policy may be read here
The following W3C standards are at least partially implemented:The Keystone Application Framework partially implements XUL (XML User Interface Language). The specification for this may be seen at:
http://www.mozilla.org/projects/xul/xul.html
This work falls under the Mozilla Public License, the terms of which may be read here
Expat (XML Parser Toolkit) is a free C Language XML parser written by James Clark, officially Technical Lead on the W3C XML Working Group. The Expat parser is used and redistributed with the Keystone source.
The official site for the parser is http://www.jclark.com/xml/expat.html
Expat is licensed (quote)
Expat is freely available with source under a very liberal license (the MIT license).
libPNG is a C library for reading and decoding the PNG (Portable Network Graphics) image format. libPNG is published with an Open Source license, the terms of which may be read here
The Open Source libPNG license specifically permits use of the libPNG library in commercial products without restriction.
The PNG image format itself is designed to be open and freely implementable (quote)The PNG image format was designed in 1995 specifically in response to the patent problems with the LZW algorithm used in GIF. To the best of the PNG group's knowledge, PNG was then--and still is--completely patent-free
zlib is a data compression format and library used (amongst other things) by the PNG image format. zlib is used by libPNG, and therefor zlib is redistributed along with libPNG in the Keystone Framework sources.
zlib is released under a free software license the terms of which may be read here
the license permits use of zlib in commercial products without restriction (quote):zlib is designed to be a free, general-purpose, legally unencumbered -- that is, not covered by any patents -- lossless data-compression library for use on virtually any computer hardware and operating system
Microsoft Visual C Compiler is a commercial product, and therefor a software developer is required to have a purchased a copy or a of this to build software for the Windows platform using the Keystone Application framework. The applications built with the compiler may be distributed on the software developers own terms, within the scope of the LGPL license which Keystone is released under.
the GNU C Compiler is published under the GPL Free Software license
GNU Make is required to build the framework and applications on all platforms. For the Win32 platform, GNU Make is redistributed with the framework
DOxygen is an automated documentation system for C/C++ source code. The Keystone Application framework API documentation is produced by DOxygen.
The documentation created as the output of DOxygen is (quote):Documents produced by doxygen are derivative works derived from the input used in their production; they are not affected by this license. [GPL]The official website for DOxygen is http://www.doxygen.org