Open Educational Resources (OER) can increase efficiency when materials are published under a license that permits the creation of derivative works (all Creative Commons licenses that do not contain the NoDerivaties (ND) condition allow this). OER can be translated into other languages and transformed into alternate formats–such as for display on mobile devices–more easily than materials published under all rights reserved copyright. MIT OpenCourseWare uses the Creative Commons Attribution-NonCommercial-ShareAlike license (BY-NC-SA). Nearly 800 MIT OCW courses have been translated into other languages, all without needing to ask permission from the copyright holder.
Bookshare is the world’s largest accessible online library for persons with print disabilities. Bookshare was awarded a grant by the U.S. Department of Education aimed at creating the first accessible versions of open digital textbooks. U.S. Copyright law permits some authorized entities to make accessible copies of books–and permits particular authorized disabled persons to access these vetted versions. This access is incredibly important, but the exception is limited, and does not apply for users outside of the United States. Open textbooks are low hanging fruit if they are released under a license that permits the creation of derivative works, because these can be more easily converted into accessible formats, such as audio and Braille refresh. No extra permissions costs have to be incurred or royalties paid for these adaptations to take place.
Source: http://creativecommons.org/tag/accessibility