[hermitcrab]

That's not correct. You can use the LGPL version of Qt to develop commercial product without paying for a license and while keeping your source proprietary. You aren't allowed to statically link Qt under LGPL, but that isn't a big deal.

[anotherevan]

Does the LGPL deal with the fact that you actually pull in a lot of Qt code in the form in header files into your actual compiled binary?

[hermitcrab]

Yes, my understanding is that including headers is not a problem for LGPL. If it was, LGPL libraries would be useless.

Note that the LGPL version of Qt doesn't contain everything the commercial version does. But there isn't a lot missing.