You bring up a good point with the Qt CLA specifying that contributions will go toward the commercial edition, but there's one very big caveat to that: The KDE-Free Qt Foundation.
The agreement between the old Trolltech and KDE e.V. is still active today, and specifies in essence that if Digia stops developing and releasing the Free edition of Qt, that the Foundation can buy out the Qt code and release it under the open-source license they prefer.
It helps to think of the overall package as being one of a quasi-BSD license: Your contributions support proprietary and Free software development, with an added escape clause to ensure the Free part can be forked if needed.
Qt CLA
The agreement between the old Trolltech and KDE e.V. is still active today, and specifies in essence that if Digia stops developing and releasing the Free edition of Qt, that the Foundation can buy out the Qt code and release it under the open-source license they prefer.
It helps to think of the overall package as being one of a quasi-BSD license: Your contributions support proprietary and Free software development, with an added escape clause to ensure the Free part can be forked if needed.