No warrantee

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.

Yenta's licensing

Yenta's copyright and license is complicated. There are several major considerations:

Yenta may not be exported outside of the United States and Canada. This is due to its use of strong cryptography, its development inside the United States, and current US law.
Yenta contains subsystems with different copyrights and licenses. This means that you must read the individual copyrights and licenses for those subsystems, as well as the overall copyright and license for Yenta.
Some of these subsystems contain patches, additional files, or large-scale changes (such as putting them under GNU autoconf/automake), which were written by Yenta's implementors. In general, patches which are confined to a single file are covered by the copyright and license of the original file, for simplicitly, even though they were not written by those original implementors. Larger-scale changes have their own copyright and license.
Yenta's license is subject to change. The overall license below is most likely an interim one, and more liberal licensing terms, possibly derived from the GNU Public License, the Mozilla Public License, the Berkeley distribution license, or the Perl Artistic license, may be instituted in the future.
The intent of the current license is to (a) satisfy the MIT Media Lab's requirements for our own intellectual property and (b) be sufficiently restrictive that Yenta may not be simply appropriated by third parties. However, since Yenta's source code must be available for public inspection, and because Yenta is intended to eventually be open-sourced (for one of a variety of definitions of open source), these licensing terms are likely to change in the near future.
If you find that Yenta's current license is too restrictive for your purposes, please send mail to bug-yenta@media.mit.edu telling us who you are, what use you intend to make of Yenta, and in what way the existing license is insufficient. We are always open to alternative licensing schemes in order to make Yenta, and the larger purposes and techniques it espouses, as available as possible.
Third parties cannot change Yenta's licensing. The license and distribution terms for any publicly available version or derivative of this code cannot be changed by anyone who does not hold the copyright for the part in question. For example, this code cannot be simply copied and put under another distribution license, including the GNU Public License.
This also means that, while Yenta's overall licensing terms may be changed when a more-permanent licensing scheme is determined, and may also be released with particular special-case licensing if someone requests us to do so and we grant that request, certain subsystems may not have their licensing terms changed at all, because those terms are dictated by the holders of those copyrights.

The multiplicity of copyrights and licenses

Because Yenta is composed of various third-party subsystems, there is no single copyright or license that covers all parts of Yenta. Rather than including the entire text describing the applicable copyright and licensing terms for each source file in the distribution, we implicitly include the correct copyright and license, according to the following algorithm:

The smallest unit of granularity in copyright or licensing is a single source file in the distribution. Each source file is licensed by one and only one license, and every part of any particular source file is covered by the same license.
If a particular source file contains copyright or licensing terms anywhere inside it (generally, this is at the front of the file), then those terms cover the file.
If a particular source file, FOO, mentions a particular other file, BAR, as containing its copyright or licensing terms, then the terms in BAR cover FOO.
Any source file which does not contain copyright or licensing terms, or a pointer to a file containing these terms, is covered by the contents of the first COPYING file found when scanning towards the root of the distribution hierarchy.
In other words, any given file in, say, App/C/SCM is covered by the COPYING file in that directory if it does not specify otherwise. Any file which says nothing about its copyright or licensing terms, and which exists in a directory which has no COPYING file of its own, will be covered by some other COPYING file closer to the root. This eventually terminates in the toplevel COPYING file for all of Yenta, which is the file you are reading right now.

The main license

These licensing terms apply to all parts of Yenta which are not third-party subsystems. Those subsystems have their own copyright and licensing terms, as explained in their source code. Please read them.

Copyright 1999 by the Massachusetts Institute of Technology. All rights reserved.
Developed by Leonard Foner, et al, at the Media Laboratory, MIT, Cambridge, Massachusetts, with partial support from British Telecom. This distribution is approved by Nicholas Negroponte, Director of the Media Laboratory, MIT.
Permission to use, copy, or modify this software and its documentation for educational and research purposes only and without fee is hereby granted, provided that this copyright notice and the original authors' names appear on all copies and supporting documentation. If individual files are separated from this distribution directory structure, this copyright notice must be included. For any other uses of this software, in original or modified form, including but not limited to distribution in whole or in part, specific prior permission must be obtained from MIT. These programs shall not be used, rewritten, or adapted as the basis of a commercial software or hardware product without first obtaining appropriate licenses from MIT. MIT makes no representations about the suitability of this software for any purpose.
It is provided "as is" without express or implied warranty.