I'm writing a Cocoa based DjVu view widgets, which use libdjvulibre that I
eventually would like to run on the iPhone. My code will be GPL and freely
available. I recently read about the latest spat between VLC and the app
My question is if all my code is GPL and publicly available, do you, the
developers of DjVuLibre have any issue with your library being used on an iOS
There is no problem as long as you comply with the requirements of the GPL.
In fact you do not even have to ask anybody (but we are still happy to
I have read many things about the apple store and the GPL.
Unfortunately I am not in position to give a binding interpretation in the
case of DjVuLibre
because DjVuLIbre includes code from multiple source and I cannot speak for
the other authors.
VLC was not the first, search for "fsf gnu go app store". As far as I
understand, Apple will drop your app as soon as it will notice it's GPL.
I've read both the app store terms, and the gpl, and as I see it, provided I
make the source available, there should be no problem.
From what I've read about the VLC spat, a single developer insisted that Apple
take down the app against the wishes of the other VLC developers.
Anyway, what I'm doing widget wise is cloning the class interfaces in Cocoa's
PDFKit. So, in essence, this will be a drop in replacement but will display
DjVu instead of PDF. PDFKit has a really well thought out api, and this way,
you could take a great app like Skip, and make it a great DjVu viewer with a
My biggest motivation is I have a bunch of djvu books, and really would like
to be able to read them on an iPad that I'll buy eventually.
I suscribe to the vlc mailing list, and followed most of the conversation. In
the end the fundamental problem is not a single developer objected. The
fundamental problem is the Apple Store license and VLC licenses are inherently
in conflict. In that the GPL states you may not place restrictions on others
redistributing GPL code and application. If you attempt to place such
restrictions, you are prohibited from distributing the application. Anyone
with a legal standing to file lawsuit can object, not just developers or the
owners of the copyright. For example, anyone who has granted a patent license
to the GPL code, could sue for patent violation. As such, until Apple changes
its license to be GPL friendly, it is very risky to use any GPL code for an
application on the Apple Store.
That said, if you are willing to take the risk, I'm in full support. I would
be very happy to have a djvu reader for my son's ipod.
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