What do I need to ship in my installer to satisy LGPL Qt terms?

Question

Hello all,

I've been staring at the LGPL for days but can't figure out how to satisfy the legal requirements with respect to redistribution.

I understand the requirements with regards to linking with/modifying Qt but specifically don't know how to (legally) bundle the Qt DLLs with our product.

Our project is a commercial application. When using the commerical Qt in the past we simply built Qt from unmodified source and then included the DLLs/SOs in our installer for placement into the install directory of the product.

It's my understanding that, assuming we do not ever modify the Qt source code, we can satify the legal requirements by:

1. Not shipping any Qt binary libraries - which means relying on our customer pre-installing them.
2. Shipping Qt libraries with our installer - which requires us to bundle the entire source tree of Qt with our product.

(1) May be acceptable for Linux installs when we can rely on APT (or similar) to do the job but would be undesirable for Windows installs. (2) Means bloating our install footprint from 15Mb to hundreds.

Is this correct?

Can we do it by simply hosting the source package on our Web site and putting a link to it inside our installed documentation?

If we built the libraries from unmodified source code, do we still need to bundle Qt's source with our product?

I've have no luck finding a truly canonical answer to this so I'd appreciate any pointers or advice.

Many thanks.

Answer 1

You can avoid shipping source code if you

1. Include LGPL text in the distribution.
2. Offer to provide Qt source code by request to anyone who has received the program from you directly (for LGPL v2.1 or earlier you're required to provide copy of source code in physical media if customer wants it, since LGPL v3 it is OK to just host it on Web)

There is a lot of useful material in GPL FAQ, if you need more information.