WotC has obviously thought deeply about what lessons to draw from 3e's OGL and how best to use ancillary material as "advertising" for the core books. Doubtless there will be some who will say WotC is unnecessarily giving away their intellectual property, dooming 5e to subpar growth and then crippling WotC when 6e eventually comes along. But they'll be wrong, at least in my view -- this will strengthen the "network" of 5e players and thereby make everyone better off than they would otherwise be.
It would be even better if they released a full-fledged OGL/SRD along the lines of 3e, rather than what amounts to a "trial edition" of the 5e product. But even a trial edition shows much more openness than WotC has displayed in the 4e era, and is at least a modest step in the right direction.
And as far as "borrowing" from Paizo is concerned -- look, whether one likes them or not, Paizo took the fundamental building blocks of Ryan Dancey's 3e insights and used them to displace the strongest brand in the industry. The concern would be if WotC continued to stick its head in the sand and not take any pages from Paizo's playbook...