your own software in C++ with Qt

[yoyeen]

hi. anyone who has built his own software using C++ with Qt? One that you did on your own, not in a team, and just did it because you liked doing it. Or maybe you sold it somewhere? :)

[writetonsharma]

what is the problem?

[Duthomhas]

You can write as much software as you like in Qt, but if you want to sell it, you must purchase a developer license. (It isn't cheap.)

[Caligulaminus]

@Duoas:
That's not quite true. You can use Qt under the LGPL.

[Computergeek01]

@ Caligulaminus: Which restricts your Authors Right's over it, and forces you to distribute the Source code. If you want a product that you can stand behind and ensure no one F's with it, then Duoas is right.

[moorecm]

I made a minesweeper with Qt. What's the question?

[Duthomhas]

@Caligulaminus
Trolltech's licensing is quite specific. If you wish to SELL software you create using Qt, you MUST BUY a developer license.

If you want to use the LGPL option, you may not SELL the software you create.

[Caligulaminus]

@Duoas:
The LGPL explicitly allows me to sell my closed source software that I linked against a LGPL-lib.
If I overlooked something please point me to Trolltechs specific rules.

Summer is coming =)

[writetonsharma]

This is not correct, in LGPL you cannot sell. selling comes under commercial license.
Even if you may sell, you will have to keep your source open.

[Caligulaminus]

I can not sell under the LGPL. But I may sell my program, even if it links to e.g. Qt.
Wikipedia agrees with me:

The main difference between the GPL and the LGPL is that the latter can be linked to (in the case of a library, 'used by') a non-(L)GPLed program, regardless of whether it is free software or proprietary software.

https://secure.wikimedia.org/wikipedia/en/wiki/LGPL#Differences_from_the_GPL

That's exactly what the 'L' is for.

[1yR4jE8b]

Nowhere in any version of any GPL license does it say you cannot sell a program written using that license, xchat for Windows is a perfect example of a commercial GPL program.

According to the LGPL you can create a proprietary application and dynamically link against the LGPL code without open sourcing your application. Said program is not considered a derivative work, thus you do not need to release the source code. If you change QT's source code then you must share the modifications, but not the source code of *your* program.

1. License Your Application Under A Proprietary License
2. Dynamically link against the LGPL QT without modifying the source of QT
3. Provide a link to the qt/nokia/trolltech website for safe measure
4. Sell your application
5. ?????
6. Profit

One of the biggest downfalls of any Gnu license, I find, is that they are confusing as hell.

EDIT: changed link to dynamically link, important distinction

[Caligulaminus]

Thanks fright. Now I know that I'm not alone;)

they are confusing as hell.

Legalese. Aren't they all?

[Duthomhas]

OK ok, you got me in a loophole. I said "sell".

Here's the specific site.
http://qt.nokia.com/products/licensing/

It is quite plain that if you want to write "proprietary and/or commercial software with Qt where you do not want to share any source code" that you must purchase a Qt Commercial Developer License.

If you use the LGPL with proprietary code and/or sell it, you must use dynamic Qt libraries (or equivalent) in addition to a few other provisions of the LGPL.

One of the biggest downfalls of any Gnu license, I find, is that they are confusing as hell.

Because they play both ends against the middle.

[1yR4jE8b]

On that site it states that for the LGPL version of QT you must provide the changes to the source code of QT and you can write a proprietary application that dynamically links to it as long as it isn't a derivative work (of QT).

So, you only need to purchase a commercial license if you don't want to share any changes to QT's source code that you make, or if you want to statically link to QT.