Licenses

Last updated 12 October 2026

Sparkle

Sparkle is the free, open-source update framework for macOS that your app includes. ReleaseKit is independent: it is not affiliated with or endorsed by the Sparkle project or its authors, whose work it builds on with gratitude.

ReleaseKit writes appcasts, signatures and delta updates in Sparkle's formats. Its delta updates are made by a port of Sparkle's BinaryDelta (SUBinaryDeltaCreate.m, SUBinaryDeltaApply.m, SUBinaryDeltaCommon.m, SPUSparkleDeltaArchive.m) and of the bsdiff Sparkle ships, used under the licenses below.

Sparkle's license (MIT)

Copyright (c) 2006-2013 Andy Matuschak.
Copyright (c) 2009-2013 Elgato Systems GmbH.
Copyright (c) 2011-2014 Kornel Lesiński.
Copyright (c) 2015-2017 Mayur Pawashe.
Copyright (c) 2014 C.W. Betts.
Copyright (c) 2014 Petroules Corporation.
Copyright (c) 2014 Big Nerd Ranch.
All rights reserved.

Permission is hereby granted, free of charge, to any person obtaining a copy of
this software and associated documentation files (the "Software"), to deal in
the Software without restriction, including without limitation the rights to
use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
the Software, and to permit persons to whom the Software is furnished to do so,
subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

bsdiff, as shipped by Sparkle

bspatch.c and bsdiff.c, from bsdiff 4.3 <http://www.daemonology.net/bsdiff/>:

Copyright 2003-2005 Colin Percival
All rights reserved

Redistribution and use in source and binary forms, with or without
modification, are permitted providing that the following conditions 
are met:
1. Redistributions of source code must retain the above copyright
   notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
   notice, this list of conditions and the following disclaimer in the
   documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.

Other software

ReleaseKit's server is written in Rust and uses open-source libraries, under the MIT, Apache 2.0 and similar licenses, run on our servers and not distributed.