 What is one limit all kinds of OA put on user freedom?
In any case, we can be more specific about which access barriers OA removes. OA removes price barriers. OA removes these permission barriers. OA makes work more useful in both ways, by making it available to more people who can put it to use, and by freeing those people to use and reuse it. While every kind of OA removes price barriers, there are many different permission barriers we could remove if we wanted to. OA was defined in three influential public statements: the Budapest Open Access Initiative (February 2002), the Bethesda Statement on Open Access Publishing (June 2003), and the Berlin Declaration on Open Access to Knowledge in the Sciences and Humanities (October 2003). Note that all three legs of the BBB definition go beyond removing price barriers to removing permission barriers, or beyond gratis OA to libre OA. But at the same time, all three allow at least one limit on user freedom: an obligation to attribute the work to the author. The purpose of OA is to remove barriers to all legitimate scholarly uses for scholarly literature, but there’s no legitimate scholarly purpose in suppressing attribution to the texts we use. The basic idea of OA is simple: Make research literature available online without price barriers and without most permission barriers. In principle, any kind of digital content can be OA, since any digital content can be put online without price or permission barriers. OA is made possible by the internet and copyright-holder consent.
 There is an obligation to credit the work to the author.
 A constraint on library privileges.  A limit on text mining.  A constraint on reproduction and distribution.  There is an obligation to credit the work to the author.