Open content materials can be viewed, used or modified freely for any purpose, but usually require attribution, and often have a ShareAlike clause allowing the content to be reused if shared under the same conditions. This is often applied through a widely known open license - for example the Creative Commons Attribution and Creative Commons Attribution ShareAlike licenses.
Some content allows only non-commercial use, but this is generally not considered to be true "open content" as it cannot be used freely for any purpose. Some content licenses have a no derivatives clause, but this is not open content, and could more accurately be called open access.
Public domain content has no restrictions whatsoever, but it is often (e.g. when adding it to Appropedia) regarded as a good thing to still give attribution to public domain content. In an academic, research or journalistic context, not giving attribution to public domain content could be regarded as plagiarism, even if it is not a copyright violation.
The best known example of open content is Wikipedia.
 Gratis and libre
Gratis means "for nothing," free of charge, even though the good or service has value.
This is sometimes explained with the phrase, "Free as in free beer".
Libre is a word in some languages (from Latin and related to "līberty"), that denotes being free, as in "freedom". The phrases "free as in free speech" and "free as in freedom" are used to explain this.
True "free content" and "free software" is both
Members of the free software community often talk about free as in free speech (libre) and free as in free beer (gratis, gratuit), as the word free in English does not distinguish between these meanings. "Free software" usually means the former.
 What free doesn't mean
A free license does not mean that the user cannot use it for commercial purposes. However, if the license has a share-alike clause (e.g. CC-by-sa or GFDL), the user who creates a derivative must license the content in the same way and cannot prevent another party from using it as they choose.
 Open content versus free content
Open content and free content have almost identical meanings, but "free" can be misunderstood to mean "no cost" (gratis).
 Searching for open content
- Appropedia's Public Domain Search - for content with no restrictions
- Creative Commons Search - for CC licensed content (using Google or Yahoo advanced search options)
- Google and Yahoo advanced searches offer permission options, which search for pages with CC license marks.
- ↑ There is the option of a non-commercial clause but such a license is widely considered as not being true "free content".
 See also
|This page is a "stub" - it needs more content.
You are invited to.