The imbibe package itself, including all R code and the interface to niimath, is copyright (C) 2020 University College London.

The Butterworth filter code in bw.{c,h} is Copyright (C) 2007 Exstrom Laboratories LLC.

The licence and copyright terms for the other components of the package are outlined below.

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As Kernighan and Plauger (ISBN-10: 0070342075, p115) noted "Floating point numbers are like piles of sand; every time you move one you lose a little sand and pick up a little dirt. " This software is designed to generate results that are negligibly different from fslmaths. Due to differences in rounding orders, orders of instructions, etc. the results may sometimes differ by a tiny amount. These tools use 32-bit and 64-bit floating point values, with accuracy that is typically far beyond that of our imaging data (where we use 12 or 16-bit analogue to digital conversion and where our signal-to-noise is low). Therefore, the computational accuracy will typically be more than sufficient for our purposes.
  http://www.freshsources.com/page1/page7/files/Sand-1.pdf


The following files are from different authors and have their own licenses

niftilib (updated to support NIfTI 2) and znzlib are public domain
  https://nifti.nimh.nih.gov/pub/dist/src/nifti2/
  http://sourceforge.net/projects/niftilib/files/latest/download

zlib is optional and includes a simple license
 https://www.zlib.net/zlib_license.html

The project can optionally be compiled with the accelerated CloudFlare zlib. Be aware that one file uses the GPL (crc32-pclmul_asm)
 https://github.com/cloudflare/zlib

On January 7, 2020 Matthew Webster said that direct copies of the fslmaths text and error messages were permitted and are not copyrighted. This allows users to have a common interface and error detection routines.

This code was written without access to fslmaths routines, and is largely based on reverse engineering. Over the years, the fsl team has done an outstanding job of describing their algorithms on the jiscmail website. In a couple instances, no public data was available to describe the algorithms, and Taylor Hanayik from the FSL group was gracious enough to write psuedo-code that allowed accurate emulation of the fslmaths functions.

The project can optionally be compiled with tensor decomposition code by Daniel Glen (2004). This was developed at the US National Institutes of Health and is not copyrighted but is provided with permission from the author.
  https://github.com/afni/afni

The rest of the code was written by Chris Rorden (2020) and is distributed using the 2-Clause BSD license. 

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Copyright <2020> <Chris Rorden>

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permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this list of 
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conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

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