saturn-tools as a whole is licensed under the following standard MIT license:

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Copyright © 2015 Bobby Bingham

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.
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Portions of this software are derived from third-party works licensed
under terms compatible with the above MIT license:

The install script (tools/install.sh) is Copyright © 2005-2014 Rich
Felker, et al, and is licensed under the above MIT license. It was
taken from musl libc.

All other files which have no copyright comments are original works
produced specifically for use as part of this software, written either
by Bobby Bingham, the main author of the software, or by one or more
contibutors. Details on authorship of individual files can be found in
the git version control history of the project. The omission of
copyright and license comments in each file is in the interest of
source tree size.

The saturn-mkboot will compile but will not produce bootable disk
images correctly without access to a "security code" binary which is
bopyrighted by Sega. This file is not distributed as part of this
package, but the README file has instructions for extracting one if
you have access to a legitimate Sega Saturn game disk.