Irrlicht and the GNU GPL

hessiess · Post by **hessiess** » Thu Jun 05, 2008 10:09 am

Can I relice my code under the GNU GPL if I am using Irrlicht? if not what other licenses are available that would not permit the use of my code in a closed source application?

CuteAlien · Post by **CuteAlien** » Thu Jun 05, 2008 10:15 am

The zlib license used by Irrlicht is compatible with the GPL. See here: http://en.wikipedia.org/wiki/List_of_FS ... e_licenses

hessiess · Post by **hessiess** » Thu Jun 05, 2008 11:19 am

OK, thanks.

rogerborg · Post by **rogerborg** » Thu Jun 05, 2008 3:11 pm

Note carefully: the zlib licensed used by Irrlicht (implicitly) allows you to also license Irrlicht under the GPL, since that's not prohibited by the zlib license.

However, what you may not do is to remove the zlib license itself from any Irrlicht source that you distribute. No way, no how.

And so the Irrlicht portion of your overall release will become dual licensed, while your app code will (presumably) be GLP only. It's up to the recipient to make sense of that Goddamn mess, i.e. whether the liberal zlib license on Irrlicht allows the recipient to simply ignore the restrictions of the additional GPL license on that source.

hybrid · Post by **hybrid** » Thu Jun 05, 2008 3:35 pm

Well, assuming that the Irrlicht code was not changed it wouldn't make sense to derive further work solely on the Irrlicht part of the app (in that case using the original Irrlicht code would be a much better option).
So it's either code that was changed inside Irrlicht, or the newly created app code which the derived work would rely on. And both would be licensed under GPL, as well as the whole app&sources.
And of course such a license merge only allows the things which are allowed under both licenses, which is why you have to use a compatible license for GPL code.

hessiess · Post by **hessiess** » Thu Jun 05, 2008 3:42 pm

Then is it posable to dynamically link to irrlicht, instead of compiling it into my application on Linux?

rogerborg · Post by **rogerborg** » Thu Jun 05, 2008 5:12 pm

hybrid wrote:And of course such a license merge only allows the things which are allowed under both licenses, which is why you have to use a compatible license for GPL code.

That depends if you interpret the combination as allowing what's permitted by both licenses or by either license.

The FSF (by which I mean Stallman) isn't even clear on this. Stallman contends that being "GPL compatible" means that you can slap a GPL license on top of (e.g.) zlib because it doesn't say that you can't, which I agree with. What he doesn't touch on is whether he believes if the original license still applies in full and in isolation. If it does, you can ignore the GPL restrictions and just re-distribute under the zilb permissiveness, which makes dual licensing it rather pointless.

Aaaaanyway...

To avoid the issue, why not license the app code as LGPL? That doesn't require you to dual-license Irrlicht, and does still give you the protection that I think you're looking for, which is to prevent your app code from being swallowed up into a closed source project and never coming out again. The LGPL is a fine license for most purposes; it does almost everything that the GPL does, except for the viral clause. Unless your goal is explicitly to propagate the GPL (and that is the FSF's goal) then the LGPL is generally sufficient.