Tc/Tk 的软件许可（Software License）

按照 http://wiki.tcl.tk/2530 的说法，这是一个类似于BSD的license，比GPL协议限制更少。

Tcl/Tk license允许“闭源”发布，即允许只发行二进制文件，而无需发布源代码。GPL协议通常要求“开源”。

Tcl/Tk license也允许用户在衍生产品中使用别的协议。GPL则通常要求用户维持同样的协议。

关于Tcl/Tk自身的协议，上述连接中，还提及了一个概要解释。

这东西是我们的。
你可以使用、修改、放弃、或者售卖这东西，只要你跟别人说明了这些协议。
如果这东西不能用，别找我们的麻烦。
我们也不保证一定会去修正这东西。
即使政府在用这东西，我们自己也可以使用、放弃、或者售卖这东西。

原文是这样的

In even simpler language:

  Paragraph 1. It's ours.
  Paragraph 2. You can use it, modify it, give it away, or sell it. But 
               only if you tell people about these terms.
  Paragraph 3. Don't sue us if it doesn't work.
  Paragraph 4. We don't have to fix it, either.
  Paragraph 5. Even if the Government uses it, we can use it
               ourselves, give it away, or sell it.

Tcl/Tk License Terms

The following terms apply to the all versions of the core Tcl/Tk releases, the Tcl/Tk browser plug-in version 2.0, and TclBlend and Jacl version 1.0. Please note that the TclPro tools are under a different license agreement. This agreement is part of the standard Tcl/Tk distribution as the file named "license.terms".

Tcl/Tk License Terms

This software is copyrighted by the Regents of the University of California, Sun Microsystems, Inc., Scriptics Corporation, and other parties. The following terms apply to all files associated with the software unless explicitly disclaimed in individual files.

The authors hereby grant permission to use, copy, modify, distribute, and license this software and its documentation for any purpose, provided that existing copyright notices are retained in all copies and that this notice is included verbatim in any distributions. No written agreement, license, or royalty fee is required for any of the authorized uses. Modifications to this software may be copyrighted by their authors and need not follow the licensing terms described here, provided that the new terms are clearly indicated on the first page of each file where they apply.

IN NO EVENT SHALL THE AUTHORS OR DISTRIBUTORS BE LIABLE TO ANY PARTY FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OF THIS SOFTWARE, ITS DOCUMENTATION, OR ANY DERIVATIVES THEREOF, EVEN IF THE AUTHORS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

THE AUTHORS AND DISTRIBUTORS SPECIFICALLY DISCLAIM ANY WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, AND NON-INFRINGEMENT. THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, AND THE AUTHORS AND DISTRIBUTORS HAVE NO OBLIGATION TO PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.

GOVERNMENT USE: If you are acquiring this software on behalf of the U.S. government, the Government shall have only "Restricted Rights" in the software and related documentation as defined in the Federal Acquisition Regulations (FARs) in Clause 52.227.19 (c) (2). If you are acquiring the software on behalf of the Department of Defense, the software shall be classified as "Commercial Computer Software" and the Government shall have only "Restricted Rights" as defined in Clause 252.227-7013 (c) (1) of DFARs. Notwithstanding the foregoing, the authors grant the U.S. Government and others acting in its behalf permission to use and distribute the software in accordance with the terms specified in this license.

BSD License

上面说的主要是Tcl/Tk自己的license terms，并提到跟BSD协议很像。

BSD协议简单概括就是

嘿，这里是源代码，随便用，出了问题别找我。