Is qt really free ?

[Mario Carugno <marioc_debian@yahoo.com.ar>]

Hi, i'm considering develop some things for Debian
using Qt, but i wan't to know if Qt is really free.
I'm not sure now, since i've read that Qt has a
'professional edition' wich is comercial, and the
version in Linux is the 'free edition'.

The key is: The free edition have all the modules of
the professional ? Can i use the Qt database library
for insance ?

Thanks

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