It does explicitly state this in the blog: "It also allows us to initiate a dialogue with commercial companies who mostly work with open-source versions of Qt.

It does explicitly state this in the blog: "It also allows us to initiate a dialogue with commercial companies who mostly work with open-source versions of Qt." Open source is free lunch. You pay for it by engaging with the community. So requiring nothing except a login for binaries, which does come at an actual cost for the company providing them, is a pretty fair deal.