I was looking at the QT-Digia site, and I found that they really try not to get people to use open source. So i thought that it would be a good game to see how many examples we can find of companies trying to downgrade open source projects or licenses.

Here's what Digia say about GPL:

LGPL and GPL are complex licenses that contain many obligations and restrictions you must abide with. Always consult an experienced lawyer before choosing these licenses for your project.[/quote]

Is it really that dangerous to develop under LGPL and GPL? On Linux, most things are GPL so I find this really weird.

I was looking at the QT-Digia site, and I found that they really try not to get people to use open source. So i thought that it would be a good game to see how many examples we can find of companies trying to downgrade open source projects or licenses.

Here's what Digia say about GPL:

LGPL and GPL are complex licenses that contain many obligations and restrictions you must abide with. Always consult an experienced lawyer before choosing these licenses for your project.

Is it really that dangerous to develop under LGPL and GPL? On Linux, most things are GPL so I find this really weird.
[/quote]

No, it is not "dangerous" (atleast not any more dangerous than software development in general) to develop under LGPL or GPL, There are however things you need to keep in mind if you're using LGPL licensed libraries in a proprietary project. (The GPL is quite simple, if you use any GPL licensed code then everything that touches that code has to be released under either the GPL or a license that grants the atleast same rights and doesn't add any additional restrictions for the end user).

As far as complexity goes both the GPL and the LGPL are reasonably straightforward compared to pretty much every single proprietary license i've seen thus far so i don't think the need to consult a lawyer is any greater with LGPL licensed libraries(Its always a good idea to consult a lawyer if you intend to distribute software in countries such as the US where the patent minefields are a big problem) unless you intend to find a way around the restrictions of the licenses.
Compared to other less restrictive opensource licenses however the GPL and LGPL are fairly complex and for proprietary development (most games are proprietary since it is very difficult to find a good businessmodel for a free software game) other licenses tend to fit much better.

When it comes to games the biggest problem with the LGPL(and GPL if you're making an opensource game) is that your end users has to be able to upgrade / replace / modify the LGPL/GPL licensed portions, on iOS and consoles they cannot do this due to the restricted nature of the platform and thus you cannot use other peoples LGPL/GPL licensd code (v3 atleast, v2 might possibly allow it but trying to take advantage of loopholes is always risky) at all on those platforms (unless you have the original authors permission), You might also have problems with copyprotection systems since they'd have to allow the use of modified libraries.

The GPL isn't the only open source license - there are others. It's wrong to equate discouragement of using the GPL with a general discouragement of open source - just pick a different open source license instead.

About the GPL itself, it has deep deep roots in a particular computing culture, and that's late-70s computing academia and the old MIT hacker culture. The entire GNU project started off as a result of restrictions on source code availability in this culture, and if you want to be brutally honest (or honestly brutal even) about it, it doesn't really have much in common with the idea of "a computer on every desk and in every home".

Why is it used so much in Linux? Well the full name of the OS should give you a clue - GNU/Linux. Linux is just the kernel; the name may have stuck but huge chunks of the OS come from the GNU project, so the GPL is naturally used.

So if you use GPL / LGPL licensed software in your application, then does your application have to be GPL as well? Because if it doesn't then obviously Digia are trying to put people off, because the resultant software doesn't need to have GPL.

If you use GPL code/libraries in your software then, unless it has some kind of runtime exception (see GCC) your software must also be GPL licensed.

If you use LGPL code/libs in your software then if you dynamically link with it (think DLLs on Windows) your code does not have to be GPL, but if you statically link then the GPL rules apply.

(Personally I wouldn't touch GPL code with someone elses keyboard and LGPL only if I really had no other choice in the matter. What code I have released over the years has been covered by the zlib license.)

So if you use GPL / LGPL licensed software in your application, then does your application have to be GPL as well? Because if it doesn't then obviously Digia are trying to put people off, because the resultant software doesn't need to have GPL.

Not quite. As phantom said, if you dynamically link to an LGPL library, you're perfectly fine and can keep your project as a closed source commercial program. Alternatively, you could technically statically link to an LGPL program and stay closed source as well, so long as you release your compiled object files so end users can re-link.

We use some LGPL libraries in some of our commercial applications at my work.

We use some LGPL libraries in some of our commercial applications at my work.

Yeah, I believe we use at least one LGPL lib (audio file related) in our build process and I wouldn't be surprised if there was one or more unmodified GPL app somewhere in the build tools either.

When it comes to games the biggest problem with the LGPL(and GPL if you're making an opensource game) is that your end users has to be able to upgrade / replace / modify the LGPL/GPL licensed portions, on iOS and consoles they cannot do this due to the restricted nature of the platform and thus you cannot use other peoples LGPL/GPL licensd code (v3 atleast, v2 might possibly allow it but trying to take advantage of loopholes is always risky) at all on those platforms (unless you have the original authors permission), You might also have problems with copyprotection systems since they'd have to allow the use of modified libraries.

I would then have a question about games ported to these systems which were previously GPL'ed. For instance, you can buy Doom on XBLA. Can you obtain and modify the code for the version of the game on XBLA, or is there some emulation of the old DOS/Windows binary?

Why is it used so much in Linux? Well the full name of the OS should give you a clue - GNU/Linux. Linux is just the kernel; the name may have stuck but huge chunks of the OS come from the GNU project, so the GPL is naturally used.

I don't quite agree. Yes, it does feels "natural" to use the GPL in open source development but why exactly? I think it just has more to do with the combined influence of Linus Torvalds and Richard Stallman over the people who promote open source, since the GPL is pretty much the only thing in which both agree.

Stallman started it, Torvalds gave it some force, and the developers went along with it. That's my view.

[quote name='mhagain' timestamp='1349718306' post='4988055']Why is it used so much in Linux? Well the full name of the OS should give you a clue - GNU/Linux. Linux is just the kernel; the name may have stuck but huge chunks of the OS come from the GNU project, so the GPL is naturally used.

I don't quite agree. Yes, it does feels "natural" to use the GPL in open source development but why exactly? I think it just has more to do with the combined influence of Linus Torvalds and Richard Stallman over the people who promote open source, since the GPL is pretty much the only thing in which both agree.

Stallman started it, Torvalds gave it some force, and the developers went along with it. That's my view.
[/quote]
I think you misunderstood him. Anything the GNU touches is generally GPL. It's a license that tends to infect and grow into projects.

That said regarding open source you'll find many people prefer the MIT license.