# CWI license
The CWI license is the license applied to early releases of Hack, as detailed here. CWI, the Centrum voor Wiskunde en Informatica, is the new name for the Stichting Mathematisch Centrum. It is a BSD-type license, and one-way (inclusion) compatible with the GNU GFDL. For the purposes of NetHackWiki, that is perfectly adequate.
NetHack 1.3d, 1.4f, 2.2a and 2.3e contain no explicit license statement, but include the line:

/* Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1985. */

which probably means the CWI license applies.

License statement
Jay Fenlason has stated:

I wish to place all of the hack source code I wrote under the following license.

&gt; /*
&gt;  * Copyright (c) 1982 Jay Fenlason 
&gt;  * All rights reserved.
&gt;  *
&gt;  * Redistribution and use in source and binary forms, with or without
&gt;  * modification, are permitted provided that the following conditions
&gt;  * are met:
&gt;  * 1. Redistributions of source code must retain the above copyright
&gt;  *    notice, this list of conditions and the following disclaimer.
&gt;  * 2. Redistributions in binary form must reproduce the above copyright
&gt;  *    notice, this list of conditions and the following disclaimer in the
&gt;  *    documentation and/or other materials provided with the distribution.
&gt;  * 3. The name of the author may not be used to endorse or promote products
&gt;  *    derived from this software without specific prior written permission.
&gt;  *
&gt;  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
&gt;  * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
&gt;  * AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL
&gt;  * THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
&gt;  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
&gt;  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
&gt;  * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
&gt;  * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
&gt;  * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
&gt;  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
&gt;  */
&gt;
                                Jay Fenlason

Furthermore, CWI has stated:

Copyright (c) 1985, Stichting Centrum voor Wiskunde en Informatica,
Amsterdam
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:

- Redistributions of source code must retain the above copyright notice,
this list of conditions and the following disclaimer.

- Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.

- Neither the name of the Stichting Centrum voor Wiskunde en
Informatica, nor the names of its contributors may be used to endorse or
promote products derived from this software without specific prior
written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Dick Broekhuis, controller CWI