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Re: [Off-topic] Licenses (Was: How to reratify the DFSG ?)

"Rev. Joseph Carter" <knghtbrd@earthlink.net> wrote:
> Qt's license says the program must be GPL or similar to use Qt free.

This is where the problem comes from, since the GPL is incompatible with Qt's 
licence, so this clause translates to ``you are not allowed to use Qt in your 
own free programs''  --- it's a Catch-22.

Why is Qt's licence incompatible with GPL ?

>From the Qt License:

  The Qt toolkit is a product of Troll Tech AS. This license is limited to
  use with the X Window System.

>From the GPL:

    b) You must cause any work that you distribute or publish, that in
    whole or in part contains or is derived from the Program or any
    part thereof, to be licensed as a whole at no charge to all third
    parties under the terms of this License.

Since a GPL'd program that makes use of Qt cannot be so licensed to someone 
wanting to use it on a non X-windows platform, the GPL prohibits it's 

Also from the Qt license:

  You may copy this version of the Qt toolkit provided that the entire
  archive is distributed unchanged and as a whole, including this notice.

and from the GPL:

    2. You may modify your copy or copies of the Program or any portion
  of it, thus forming a work based on the Program, and copy and
  distribute such modifications or work under the terms of Section 1
  above, provided that you also meet all of these conditions:

Q.E.D.  The ``distributed under the GPL'' clause of the Qt licence is invalid.

I don't know how this works in the USA, but IIRC in the UK a contract with an 
invalid clause is deemed invalid as a whole.  If this is the case, Qt does not 
in fact have a licence for use as freeware, so either you're no allowed to use 
it at all, or you can do what the hell you like with it --- I leave the 
decision to you and your lawyers.

I won't be touching it in a hurry though.

Cheers, Phil.

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