Once content has been created in a tangible form, it is automatically copyrighted under US law. Content creators may choose to "open" their content in order to provide others with permission beforehand. If materials are listed as open, then they may be used freely without requesting permission or paying a fee. Many open access content has a license applied to it, which requires certain conditions in exchange for use of the content (ie. attribution, non-profit use).
Open content does not necessarily mean free content. The key point is that open materials are open for distribution.
Copyright
Copyright holders have exclusive rights to create reproductions, to create derivative works, to distribute and to perform publicly. Once an item has been created in a “stable,” tangible form, then it is automatically copyrighted. Registering for copyright provides extra security and exclusion, but it is not required for an item to be copyrighted.
Patents
Patents are a documentation that secures for a term of years the exclusive right to make, use, or sell an invention.
Public Domain
Content that is in the public domain have intellectual property rights that have either expired or are inapplicable.
Fair use is an exception that allows use of small portions of copyrighted materials for the following reasons:
• Criticism
• Comment
• News reporting
• Teaching
• Scholarship
• Research
Below is a list of legitimate, vetted depositories of open source documents ranging a wide variety of subjects.
A open-access archive for scholarly articles in the fields of physics, mathematics, computer science, quantitative biology, quantitative finance, statistics, electrical engineering and systems science, and economics. Materials on this site are not peer-reviewed by arXiv.
Complete digitized back runs of core scholarly journals.
Provides access to electronic journals issued by Japanese academic institutions available to the public at no cost.
Public Domain, Fair Use and Open Resources found online.