The entire point of the LGPL is to give closed source applications access to an open-source library in a way that maintains the freedom of the library. Specifically, the user of the application must be able to change the LGPL library and have the application use it.

To achieve this, the LGPL gives you a few options for compliance. I am not a lawyer, but I believe that all of them are incompatible with iPhone apps delivered legally through the AppStore. I will lay out my reasoning here:

Section 4d gives two options for compliance: Either provide the source or object files suitable for relinking (4d0) or use a shared library (4d1).

Shared libraries are out, because Apple does not permit their use in the AppStore.

Section 4d0 is a little more complicated. For an application targeted to a PC or Mac, it would be easy to comply by just packaging up your .o files, the LGPL library, a makefile, and documentation. However there are subclauses in section 4 that make me believe that there is no way to comply on the iPhone. Specifically:

Section 4d0 not only specifies that you must convey the minimal source and object files, but you must also provide terms. Together they must “permit the user to recombine or relink the Application with a modified version of the Linked Version to produce a modified Combined Work”

Section 4e requires that you provide instructions that allows someone to change the LGPL portions, create a new combined work and install and execute that combined work.

To do either of these things, the user would need to be enrolled in Apple’s developer program which costs $99/year. These terms are implicitly part of your terms, meaning that it’s basically equivalent to you charging $99/year for the user to make modifications.

The GPL allows you to charge what you want to convey the Combined Work to begin with, but section 10 of the GPL (which I think still applies to the LGPL) states:

You may not impose any further restrictions on the exercise of the rights granted or affirmed under this License. For example, you may not impose a license fee, royalty, or other charge for exercise of rights granted under this License.

Now, obviously, being able to develop isn’t free, but those costs are not as directly related to exercising your rights as the $99/year is. Specifically, you cannot create an executable or put in on a device without the certificates you obtain from the program.

Here’s an alternative view from Huy Zing — I think the “Spirit of the LPGL” section in the blog is actually required by the text of the license.

Here’s a discussion on the cocos2d forum about switching away from LGPL. They tried adding to the license at first and then moved to an MIT license.

I haven’t been able to find any official ruling on gnu.org, so I will write them and see if they can add to their FAQ (as they did for Java when it was an issue).

Get iPhone programming tips in your inbox with my Beginner iPhone Programming Tips newsletter.