An open content license relies on copyright law to establish rules that ensure content can be shared, verified, attributed and credentials of authors, if any are required, are maintained as metadata in documentation. The rules vary according to the specific domain, e.g. open science differs from open configuration.
Unlike FOSS or open source, open content requires the "sticky", "viral", required-reintegration attribute common to free software and other share-alike licenses. Documentation differs from software in several ways:
- documentation cannot be checked as easily by simply using it, and it contains assertions about the opinions or instructions claimed to come from some trusted source - accordingly allowing arbitrary change to it is likely to be disastrous, resulting in libel in some cases or at least abuse of someone's repute
- documents can be edited by a much larger number of people and there is no way to check their integrity beyond a spell check and grammar check, so without the commitment to re-integrate, versions will proliferate to chaos
- credits, credentials and attribution are critical to the trust of the user of the documentation, unlike software where test suites and quality control can be more rigorized
Some misguided attempts to apply the DFSG to open content have been made. They fail for the reasons above. The GFDL, CC-by-sa, CC-by-nc-sa licenses do not satisfy the DSFG and they should not, they satisfy constraints common to share-alike projects such as a consortium or industry standard. A reasonable comparison is to Java and Sun's use of trademarks to prevent Microsoft from releasing bogus incompatible Java.
The use of open content often requires some advocacy. For instance, documentation for a proprietary extension to open source software might be made open content or not: if it is, the specification can spread to others and there may be free extensions.