any chance D7 will use DU license strategy?

I think it would be nice to be able to use D7 core for free just like DU and just buy the modules I need. I really only need videos and photos. Then I could use D7 on more sites along with DU.

You are already able to use D7 without license. The only difference is the presence of "powered by" link in D7 without license and a pop-up appers only to administrators. 

The question was asking if D7 would be free without attribution, and one would buy the modules as in DU.

My guess would be that Boonex would not change the current licensing model for Dolphin Classic.  However, that would be for Boonex to say, I am just guessing the answer.

Well, I told that because D7 (with all his modules) is basically free. You need a license only to remove "Powered by" link. Change license "model" for D7 would be a bad thing for users.