qt 4.5 and above license issue..

[chaoticbob]

...in regards to the first part of your question...

According to the Qt License FAQ - you cannot switch from LGPL to commercial:
http://www.qtsoftware.com/about/lice...-i-switch-from

Can I switch from using Qt under the LGPL to commercial afterwards?

Users of the LGPL versions of Qt need to comply with the LGPL licensing terms and conditions. Qt’s commercial license agreement contains a restriction that prohibits customers from initially beginning development with the LGPL licensed version of Qt and then transitioning to a commercial version of Qt.

The Qt commercial license is based on a yearly support contract after the initial purchase. That means you pay up front the cost of the license and you renew each year based on the support cost. I can't remember the pricing for it right now - it's on their website or you need to inquire from one of the sales people.