Under what license(s) are Tcl and such accessories as [Tk], [Expect], [tcllib], ... available?
Is it possible/practical/easy/... to use Tcl in commercial products?
Is the Tcl license compatible with GPL?


The answers are ...
[[very liberal, and so forth]]

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Each author is free to use whatever license s/he wishes.
The TCT encourages people to use a [BSD]-related license similar to the one used in Tcl/Tk/tcllib/tklib/etc. as some companies find it less restrictive than [GPL] or [LGPL].
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The license for the standard Tcl distribution is

http://purl.org/tcl/home/software/tcltk/license_terms.html
.
[Kbk] writes in comp.lang.tcl the following summary of the Tcl license:

 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.


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[[lots more details]]

It is recommended that before you begin working with an extension or application you
take a look over the license included.  If a license is not available, you may want to attempt to get some sort of license in writing so as to ensure that you don't encounter any surprises in the future.


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If you are a software author, you should think carefully about what kind of
end user license agreement (or [EULA] in legal parlance) you use.  However,
as [David Welton] mentioned recently in comp.lang.tcl, 
http://www.dina.kvl.dk/~abraham/rants/license.html makes a strong argument
against developers trying to invent their own licenses.

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If you are not religiously convinced that one license is perfect for everything, you might consider what category your work falls under and how you want people to use it:

   * '''Application''' - a useful, complete application that does something for an end user.  Both GPL and BSD style licenses work here, depending on whether you are worried about someone else adding some proprietary changes to your code and releasing it publically.

   * '''Library''' - some code that by itself is not useful, but can be combined with other libraries and code to create an application.  The BSD or at least LGPL would be much appreciated by your fellow developers so they can use the code, even in proprietary projects, without worries.

See also [Open Source].

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'''Minimal licences'''

   * [NOL] No Obligation Licence
   * [OLL] One Line Licence
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'
[Lars H]: Could anyone natively English-speaking comment on the two spellings 
"licen'''c'''e" 
and 
"licen'''s'''e"? 
Looking in a printed dictionary (these tend to be more reliable than the net in such matters) I find "licence" listed primarily as a noun, whereas "license" is only listed as a verb. Yet I see both used as nouns all over!

Webster's Revised Unabridged Dictionary (1913)
License \Li"cense\ (l[imac]"sens), n. [Written also licence.]
   [F. licence, L. licentia, fr. licere to be permitted, prob.
   orig., to be left free to one; akin to linquere to leave. See
   Loan, and cf. Illicit, Leisure.]
   1. Authority or liberty given to do or forbear any act;
      especially, a formal permission from the proper
      authorities to perform certain acts or to carry on a
      certain business, which without such permission would be
      illegal; a grant of permission; as, a license to preach,
      to practice medicine, to sell gunpowder or intoxicating
      liquors.

            To have a license and a leave at London to dwell.
                                                  --P. Plowman.

   2. The document granting such permission. --Addison.

   3. Excess of liberty; freedom abused, or used in contempt of
      law or decorum; disregard of law or propriety.

            License they mean when they cry liberty. --Milton.

   4. That deviation from strict fact, form, or rule, in which
      an artist or writer indulges, assuming that it will be
      permitted for the sake of the advantage or effect gained;
      as, poetic license; grammatical license, etc.

   Syn: Leave; liberty; permission.

WordNet (r) 2.0
licence

     n 1: excessive freedom; lack of due restraint; "when liberty
          becomes license dictatorship is near"- Will Durant; "the
          intolerable license with which the newspapers
          break...the rules of decorum"- Edmund Burke [syn: license]
     2: freedom to deviate deliberately from normally applicable
        rules or practices (especially in behavior or speech)
        [syn: license]
     3: a legal document giving official permission to do something
        [syn: license, permit]
     v : authorize officially; "I am licensed to practice law in this
         state" [syn: license, certify] [ant: decertify] 

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[Category Deployment]
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[Category Licence]