Posting materials to Sakai, or any course management system, still requires the instructor to comply with Copyright Law. There are many considerations in determining fair use, each instance should be assessed on its own merits. However broadly speaking, non-licensed, copyrighted works will require permission.
One instrument that is helpful in determining if you have met the standard for Fair Use is Colombia University's fair use checklist. If the fair use analysis leads you to believe that reserve use isn't fair, you need to ask for permission.
Booth Library provides access to a number of databases and electronic sources (i.e. journal articles and eBooks) through agreements with vendors. Database licensing does not permit downloading a .pdf of the e-source to a course management system.
When posting links to copyrighted material in Sakai or any course management system, it is recommended the instructor post a notice to students cautioning them not to distribute or use the material outside of the course.
For example:
United States law governs the use of copyrighted material. These laws prohibit reproduction of the material for purposes other than the intended instructional purposes of this course. Other uses, including commercial use and any further electronic distribution of the material, may constitute copyright infringement.