 What is one limit all kinds of OA put on user freedom?
Open access (OA) literature is digital, online, free of charge, and free of most copyright and licensing restrictions. In any case, we can be more specific about which access barriers OA removes. OA removes price barriers. Copyright can also be a significant access barrier. 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. If we remove price barriers alone, we provide gratis OA , and if we remove at least some permission barriers as well, we provide libre OA . 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). I sometimes refer to their overlap or common ground as the BBB definition of OA. For a work to be OA, the copyright holder must consent in advance to let users “copy, use, distribute, transmit and display the work publicly and to make and distribute derivative works, in any digital medium for any responsible purpose, subject to proper attribution of authorship.” 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. (That’s why my shorthand definition says that OA literature is free of “most” rather than “all” copyright and licensing restrictions.) The basic idea of OA is simple: Make research literature available online without price barriers and without most permission barriers. If there are complexities, they lie in the transition from where we are now to a world in which OA is the default for new research. 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. Second, scholarly journals generally don’t pay authors for their research articles, which frees this special tribe of authors to consent to OA without losing revenue.
 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.