Calibre API for Mobi conversion

[Sebadub]

Is there a way to integrate in 3rd party software, some of the Calibre API? We are interested in offering conversion to Mobi from within our eBook Publisher software. Is there a model in place to benefit of some of the Calibre modules?

[chaley]

The first thing to think about is calibre's license, which is GPL V2. Almost any integration of calibre other than using it as a separate binary (e.g., using its command line) will require your app also to be licensed under the same terms. Consequence: you would need to be prepared to publish the source code of your application.

[kovidgoyal]

GPL v3 not v2 and even if you use the binaries, you will still need to open source your product, as required by the GPL. If you are willing to do that, then you can bundle calibre with your software and use the ebook-convert tool to do the conversions.

[chaley]

@Kovid: according to http://www.gnu.org/licenses/gpl-faq....prietarySystem someone could distribute calibre along with a proprietary program as long as no claim is made that calibre is "part of" the proprietary program and they "communicate at arms length". This permits someone to ship a calibre "binary" separate from the proprietary app and for the proprietary app to use its command line interface.

Of course, the person must be clear about what they are doing to avoid implicit license inclusion. Quoting from the above link:

If people were to distribute GPL-covered software calling it “part of” a system that users know is partly proprietary, users might be uncertain of their rights regarding the GPL-covered software. But if they know that what they have received is a free program plus another program, side by side, their rights will be clear.

[kovidgoyal]

See the next paragraph in the FAQ you posted:

The difference between this and “incorporating” the GPL-covered software is partly a matter of substance and partly form. The substantive part is this: if the two programs are combined so that they become effectively two parts of one program, then you can't treat them as two separate programs. So the GPL has to cover the whole thing.

It does not matter if you interface with a GPLv3 program by calling a binary or by loading a dll, as long as you present the resulting program as one program the GPL applies.