Some code carries the Zope Public License (as indicated in the comments):

Zope Public License (ZPL) Version 2.0

This software is Copyright (c) Zope Corporation (tm) and Contributors. 
All rights reserved.

This license has been certified as open source. It has also been designated as 
GPL compatible by the Free Software Foundation (FSF).

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

* Redistributions in 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. 
* The name Zope Corporation (tm) must not be used to endorse or promote 
  products derived from this software without prior written permission from 
  Zope Corporation. 
* The right to distribute this software or to use it for any purpose does not 
  give you the right to use Servicemarks (sm) or Trademarks (tm) of Zope 
  Corporation. Use of them is covered in a separate agreement 
  (see http://www.zope.com/Marks). 
If any files are modified, you must cause the modified files to carry prominent 
notices stating that you changed the files and the date of any change. 

Disclaimer
THIS SOFTWARE IS PROVIDED BY ZOPE CORPORATION ``AS IS'' AND ANY EXPRESSED 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 ZOPE CORPORATION OR ITS 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.

This software consists of contributions made by Zope Corporation and many 
individuals on behalf of Zope Corporation. Specific attributions are listed 
in the accompanying credits file.
