Terms and Conditions
Text equivalent to the following appears at the end of every SOFA routine (with one exception).
There are small formatting differences between the Fortran and C versions.
The one exception is the "leap second" routine DAT. This uniquely is classified as
"user replaceable", and has a mitigated license statement that permits the distribution
of local variants under the same name. This measure allows other SOFA routines to call
the local variant, which may be file or network based, or otherwise equipped to pick up
IERS leap second updates with no need to download new SOFA code.
The copyright of the SOFA Software belongs to the Standards Of Fundamental
Astronomy Board of the International Astronomical Union.
SOFA Software License
By using this software you accept the following six terms and conditions
which apply to its use.
- The Software is owned by the IAU SOFA Board ("SOFA").
- Permission is granted to anyone to use the SOFA software for
any purpose, including commercial applications, free of charge and without
payment of royalties, subject to the conditions and restrictions listed below.
- You (the user) may copy and distribute SOFA source code to
others, and use and adapt its code and algorithms in your own software, on
a world-wide, royalty-free basis. That portion of your distribution that
does not consist of intact and unchanged copies of SOFA source code files
is a "derived work" that must comply with the following requirements:
- Your work shall be marked or carry a statement that it (i)
uses routines and computations derived by you from software provided by
SOFA under license to you; and (ii) does not itself constitute software
provided by and/or endorsed by SOFA.
- The source code of your derived work must contain descriptions
of how the derived work is based upon, contains and/or differs from the
original SOFA software.
- The names of all routines in your derived work shall not
include the prefix "iau" or "sofa" or trivial modifications thereof such
as changes of case.
- The origin of the SOFA components of your derived work must
not be misrepresented; you must not claim that you wrote the original
software, nor file a patent application for SOFA software or algorithms
embedded in the SOFA software.
- These requirements must be reproduced intact in any source
distribution and shall apply to anyone to whom you have granted a further
right to modify the source code of your derived work.
Note that, as originally distributed, the SOFA software is intended to
be a definitive implementation of the IAU standards, and consequently
third-party modifications are discouraged. All variations, no matter how
minor, must be explicitly marked as such, as explained above.
- You shall not cause the SOFA software to be brought into
disrepute, either by misuse, or use for inappropriate tasks, or by
- The SOFA software is provided "as is" and SOFA makes no
warranty as to its use or performance. SOFA does not and cannot warrant
the performance or results which the user may obtain by using the SOFA
software. SOFA makes no warranties, express or implied, as to
non-infringement of third party rights, merchantability, or fitness for
any particular purpose. In no event will SOFA be liable to the user for
any consequential, incidental, or special damages, including any lost
profits or lost savings, even if a SOFA representative has been advised
of such damages, or for any claim by any third party.
- The provision of any version of the SOFA software under
the terms and conditions specified herein does not imply that future
versions will also be made available under the same terms and
In any published work or commercial product which uses the SOFA
software directly, acknowledgement (see www.iausofa.org) is appreciated.
Correspondence concerning SOFA software should be addressed as follows:
- IAU SOFA Center
- HM Nautical Almanac Office
- UK Hydrographic Office
- Admiralty Way
- Taunton, TA1 2DN
- United Kingdom
Acknowledgement & Citation for SOFA
If your use of SOFA results in a publication, presentation or product, please
include a citation. Evidence of your use of the SOFA libraries is necessary to
ensure continuing support of the initiative.
The following is a suitable form of words: “Software Routines from
the IAU SOFA Collection were used. Copyright © International Astronomical
Union Standards of Fundamental Astronomy (http://www.iausofa.org)”.
A BibTeX file is available.