LGPL and app store [LWN.net]

LGPL and app store

Posted Nov 23, 2012 8:28 UTC (Fri) by epa (subscriber, #39769)
In reply to: LGPL and app store by khim
Parent article: Relicensing VLC from GPL to LGPL

Have a look at section 6 of LGPL 2.1. If you distribute a program that uses the library you must provide a way for the user to relink it with a modified version of the library.

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LGPL and app store

Posted Nov 23, 2012 14:54 UTC (Fri) by khim (subscriber, #9252) [Link] (1 responses)

Have you looked on said part?

You must do one of these things:
…
Use a suitable shared library mechanism for linking with the Library. A suitable mechanism is one that (1) uses at run time a copy of the library already present on the user's computer system, rather than copying library functions into the executable, and (2) will operate properly with a modified version of the library, if the user installs one, as long as the modified version is interface-compatible with the version that the work was made with.
…

If user can somehow install library then it must be used. If user have no means to install the library, then it's user's problem, not a developer's problem. That's why I've said "it's your problem, really": LGPL2.1 does not cover this case at all.

LGPL and app store

Posted Nov 23, 2012 16:15 UTC (Fri) by epa (subscriber, #39769) [Link]

Yup, it says that if the user installs a modified library then it must be used. You can argue that the letter of the licence doesn't exclude technological measures to stop the user from installing a modified library, so you can ship the code on a locked-down device to prevent the user from having freedom to change the library despite what the licence says. This is the problem that newer GPL and LGPL versions address.

However I think the spirit and intent of the licence is that the user has freedom to modify the library (as explained in the LGPL's preamble). This is why I wrote in my original post still violates the spirit of the licence, if perhaps not the letter.

Licensing VLC under LGPL rather than GPL doesn't avoid this problem. You are still going against the intent of the licence by distributing via a locked-down app store. You mentioned linking against Apple's proprietary DRM components, which is more likely to be the reason they did it.