Both code bases are under the LGPL, it is just that in Qt there's an extra option thanks to Digia - for those who pay for it, of course. That payment flows back into Qt as extra money.
This is the same situation as at ownCloud - without ownCloud Inc. there would simply be less development. Otherwise, it would still be aGPL so nobody loses.
Essentially, Rahul, what you portray as a 'problem' is an advantage for the ecosystem. Thanks to the proprietary license, companies like BMW and other large users of Qt contribute (via paying Digia). They would otherwise not or very little, as Open Source just isn't their thing.
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