S4 is copyright (c) 2009-2014, Stanford University.
S4 is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with this library; if not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. You can also find it on the GNU web site:
The files cubature.c and cubature.h were taken from Stephen G. Johnson’s Cubature package. See the page for details.
The files sort.c and sort.h were taken from Rusty Russell’s modification of the original libc routines. See the CCAN page for details.
The file predicates.c is public domain, written by Jonathan Richard Shewchuk. See the Quake project page for details.
Distributed with S4 is the Kiss FFT library. It is copyright (c) 2003-2014 by Mark Borgerding.
As a clarification, we should note that Lua script (.lua) files, written by the user (i.e. not containing code distributed with S4) and loaded at runtime by the S4 software, are not considered derived works of S4 and do not fall thereby under the restrictions of the GNU General Public License.
In addition, all of the example Lua code in these pages, as well as the example Lua files in the examples/ directory, may be freely used, modified, and redistributed, without any restrictions. (The warranty disclaimer still applies, of course.)