I am planning on starting a free software project in C that deals with creating maps of astronomical data; as such, I will be working very frequently with FITS files. One of the best libraries for manipulating FITS files is CFITSIO for C, but I am somewhat concerned regarding licensing. I'm planning on using the GPL license for my project, and I am aware that the FSF does not see NASA's Open Source License v1.3 as "free"; however, it appears CFITSIO doesn't use this license and instead uses the following license:
Copyright (Unpublished-all rights reserved under the copyright laws of the United States), U.S. Government as represented by the Administrator of the National Aeronautics and Space Administration. No copyright is claimed in the United States under Title 17, U.S. Code.
Permission to freely use, copy, modify, and distribute this software and its documentation without fee is hereby granted, provided that this copyright notice and disclaimer of warranty appears in all copies.
THE SOFTWARE IS PROVIDED 'AS IS' WITHOUT ANY WARRANTY OF ANY KIND, EITHER EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING, BUT NOT LIMITED TO, ANY WARRANTY THAT THE SOFTWARE WILL CONFORM TO SPECIFICATIONS, ANY IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, AND FREEDOM FROM INFRINGEMENT, AND ANY WARRANTY THAT THE DOCUMENTATION WILL CONFORM TO THE SOFTWARE, OR ANY WARRANTY THAT THE SOFTWARE WILL BE ERROR FREE. IN NO EVENT SHALL NASA BE LIABLE FOR ANY DAMAGES, INCLUDING, BUT NOT LIMITED TO, DIRECT, INDIRECT, SPECIAL OR CONSEQUENTIAL DAMAGES, ARISING OUT OF, RESULTING FROM, OR IN ANY WAY CONNECTED WITH THIS SOFTWARE, WHETHER OR NOT BASED UPON WARRANTY, CONTRACT, TORT , OR OTHERWISE, WHETHER OR NOT INJURY WAS SUSTAINED BY PERSONS OR PROPERTY OR OTHERWISE, AND WHETHER OR NOT LOSS WAS SUSTAINED FROM, OR AROSE OUT OF THE RESULTS OF, OR USE OF, THE SOFTWARE OR SERVICES PROVIDED HEREUNDER."
I have a hunch that this ticks off the boxes for a free software license, but I am unsure. I'd appreciate any advice.