From kde-licensing  Mon Sep 13 16:59:08 1999
From: David Johnson <djohnson () acuson ! com>
Date: Mon, 13 Sep 1999 16:59:08 +0000
To: kde-licensing
Subject: Re: HOW TO DEVELOP COMMERCIAL SOFTWARE
X-MARC-Message: https://marc.info/?l=kde-licensing&m=94950776505196

mao wrote:
> 
>     I know that if I use qt free edition I must to release my softwares as
> free and open source and if I use qt professional edition I can release my
> softwares as commercial and shareware.
> 
>     I want to know how can I release commercial softwares if I use KDE
> library, because I want to buy qt professional edition and develop KDE
> applications, but I would like to use KDE library. Is it possible? How?
> 
>     greetings,
> 
>     Márcio Andrey Oliveira ell

There is a difference between proprietary and commercial software, but
it's one that not many people make outside of the Free Software world.
In a nutshell, commercial software is software that is sold. Proprietary
software is software that is sold, and has no source code available for
it.

Most KDE libraries are licensed under the LGPL, which means that you can
link them to a commercial or proprietary program. So, yes, you can.

You may want to look at the QPL for licensing your own product. The
advantages for commercial software are two. First, it will still be
"Free Software", and you won't incure the wrath of Free Software
Fanatics, and you get the benefits of people sending you bug fixes and
enhancements without having to do them all yourself. Second,
modifications to your program can only be in the form of a patch, so you
still retain control of its distribution.

David Johnson