matcap_licenses.txt

with regards to most of the jpg images.
 https://github.com/martijnberger/blender/tree/master/release/datafiles/matcaps
 These matcap images are licensed as GNU GPL 2 or later, like the rest of Blender's code.
 Thanks to Kent Trammell, Aidy Burrows, John Herreno , Terry Wallwork and David Silverman for making the pictures.

cortex and red plastic matcaps from
 http://www.alecjacobson.com/weblog/?p=4827

remaining matcaps from
 https://devtalk.blender.org/t/call-for-content-matcaps/737/203