Just because a work is publicly accessible, available for anyone to read or download on the Internet, doesn't mean it's in the public domain, or not subject to copyright protections. In fact, those two concepts have nothing to do with one another.
Nearly all work published on the Internet is subject to copyright protections.
Copyright applies to all "original works of authority" as soon as they are fixed in some tangible form of expression. As soon as you click save or publish, you have created a copyrighted work, and you own the copyright on that work until or unless you give, sell, or sign some or all those rights over to someone else.
Every work of original creation that is written, recorded, notated, drawn, photographed, or otherwise captured - including a work published on the Internet - is protected by copyright.
Not all educational or noncommercial uses automatically qualify as fair use.
The law sets out purposes and factors to be considered when judging whether a use is fair or infringing, the ultimate judgment would lie in a court's interpretation.
Examples of activities that courts have found fair include*:
In the same document, the Copyright Office explains that "[t]he distinction between fair use and infringement may be unclear and not easily defined. There is no specific number of words, lines, or notes that may safely be taken without permission. Acknowledging the source of the copyrighted material does not substitute for obtaining permission."
Fair use may be a defense against infringement claims for a one-time use of a limited amount of material used for teaching, scholarship, or research, if you don't have time to receive permission in advance of use. However, you should always attempt to obtain permission from the rightsholder if you will be copying significant portions of the work, redistributing it, or creating a new work based upon it - and you should document your attempt to get that permission before using the material.
Fortunately, here at the Health Science Center, you have a couple of alternatives that you can use to avoid the need to seek permission:
*Register of Copyrights, 1961, quoted in US Copyright Office FL-102, 2009
Since 1989, a copyright notice is not required for a work to be covered by copyright protection.
Registering copyright with the US Copyright Office gives rights holders the option to pursue damages in court for infringement, but it is not required for a work to be protected by copyright. All original works of authorship are protected by copyright as soon as they are fixed in tangible form, whether or not they include a notice or are registered.
Even out of print items are subject to copyright protections for a certain period. That amount of time has varied through the years, but in the US, nearly all works published since 1923 are still under copyright protection.
Current works will not enter the public domain for a long time: works published since 1978 are generally subject to copyright protections until 70 years after the author's death.
This document from the Cornell Copyright Information Center breaks down the duration of copyright under US law for different works and circumstances.
Generally, authors own the copyrights on works they create. However, authors sometimes sign publication agreements with publishers without reading and negotiating them carefully. Some publication agreements involve the transfer of rights from the author to the publisher, which could prevent the author from copying or distributing the material in some cases.
It's important to always read and understand publication agreements before signaling them, and to negotiate them with publishers if the terms are unfavorable.