GPL license questions
 

I know you're not lawyers but some of you probably know more about GPL than me, so here's my questions. Please don't answer at all unless you're really pretty sure:

Can I make a new open source GPL app that uses chunks of code from other GPL apps?

In other words, is all GPLed code- functions, libraries, etc., fair game for other GPL apps to freely copy and use?

also:

Is it ok to write GPL plug-ins for proprietary apps? Like could I write a GPLed filter plug-in for Photoshop? So, the plug-in would be open source but the app it plugs into isn't. (Let's pretend that Adobe was ok with that- would GPL allow that?)

thanks

Re: GPL license questions
 

YES... as long as they comply with the terms of the license...

I'm not a lawyer, but here is my understanding:

Adobe is probably OK with you writing an open source free plugin, but GPL would at least prevent them to bundle or even distribute your plugin without opensourcing and GPL'ing photoshop code itself, which they certainly strongly object ...

GPL forbid to distribute GPL code linked with non GPL code, even open source, this is sometime called the GPL "viral effect". This is what is preventing GPL'd Linux drivers to be incorporated in *BSD or Solaris kernels.
GPL v3 is even going further, as code need to comply with "future" versions of the GPL, whatever they are !

For this kind of plugin development, there are many OSI license that seem more suitable:

BSD, mozilla, apache, MIT, Sun CDDL, IBM's CPL or LGPL ...

That said, it looks like there are many photoshop plugins available on the web that are distributed under the GPL license, but as they are not distributing photoshop, this is perhaps allowed by the license ... better ask your lawyer if you want to do it yourself !

Thanks. So it looks like nothing prevents adobe from distributing the GPLed plugins, as long as they don't bundle them on the photoshop disc that they're charging money for. They would have to seperately make the GPLed plugins available, on the adobe web site, for free (along with the source). And then I think everyone's legally happy.

So like, the adobe web site could say:

Here is Photoshop, download it for $299 click here. photoshop.zip

And here are some GPL plugin filters (which aren't in the $299 zip file), you can download these for free. And here's the source too. gplfilters.zip

I wouldn't bet the GPL really allow the non GPL code owner to distribute GPL code, even unbundled ...

In fact, the opposite already happen, Donald Becker, a famous linux network driver developer, once challenged Sun for distributing code allowing to reuse his GPL'd drivers on Solaris (Driver Porting Kit), this code was pulled out by Sun.

Perhaps Becker's interpretation of the GPL was too restrictive, but Adobe is probably safer in distributing no GPL code at all.

As I wrote before, LGPL and other are likely OK.

Again, I'm not a lawyer, don't trust me or anyone else on a forum for legal issues ...

There;s currently a Slashdot post running on this topic

http://linux.slashdot.org/linux/05/0...&tid=8&tid=106

Er, ok, the GPL does allow the non GPL code owner to distribute GPL code, that I know.

http://www.gnu.org/copyleft/gpl.html

First thing in the terms:

Sure I agree with you, this article say it is allowed, but you have to read the whole thing.

My point here is concerning the case where the GPL code is not standalone, but can only run when linked with the non GPL code, and this is definitely applying to plug-ins.

2.b is tellingIf there was no problem, then the LGPL wouldn't have been created.

No, I don't get it- so you're saying that a plug-in for a commercial app can't be GPL?

So those photoshop filters that are GPL (not LGPL) are incorrectly GPL and need to change their license?

The commercal app (photoshop) itself, is *not* "derived" from any plug-in, "in whole or part". Photoshop can run without the plugin.

I didn't wrote that.
I just think Adobe cannot distribute a GPL'd plug-in.
That would be a good idea, interpretations of the GPL may also forbid such distribution.
The problem here is the plug-in can't run without Photoshop.

From the LGPL license:

When a program is linked with a library, whether statically or using a shared library, the combination of the two is legally speaking a combined work, a derivative of the original library. The ordinary General Public License therefore permits such linking only if the entire combination fits its criteria of freedom. The Lesser General Public License permits more lax criteria for linking other code with the library.

I appreciate your responses but I completely don't understand you!

1. Yes or no: Can someone write a GPLed (not LGPL) photoshop filter without violating GPL?

2. Why can't adobe distribute a GPLed filter, if they distribute it for free, seperate from adobe photshop- not on the photshop CD, not for a fee, but for free? The GPL doesn't make any exemptions about who can distribute GPL code, it only says that you can't distribute GPL code *along with* a commercial application. If adobe distributes GPL plugins seperately, for free, then how have they violated GPL?

What you and most of the rest of us do not completely understand, it is the GPL and LGPL ...
I suspect all these texts written by lawyers to be ambiguous on purpose ...
I think no. he/she'd rather use a non viral license.
They have probably violated the GPL, as the result would be a mixture of GPL and non GPL code, which is illegal as the LGPL excerpt I posted previously is telling.

After a deeper reading of the GPL, and specially its last words, the answer is clearly no, you cannot distribute a GPL photoshop plugin without violating this license.

This General Public License does not permit incorporating your program into proprietary programs. If your program is a subroutine library, you may consider it more useful to permit linking proprietary applications with the library. If this is what you want to do, use the GNU Lesser General Public License instead of this License.