Open Access: Green and Gold Road OA

In Green Road Open Access, the article is published in any journal. The author retains copyright and is permitted to put copies of the article (sometimes a preprint or a postprint, sometimes the published version) in a repository or on their own web site. 

Since these journals are not Open Access to begin with, some charge authors a fee to retain copyright and make the article Open Access.

The author may receive funding from their institution or research grant to pay the author fees. 

Preprint - not peer reviewed or typeset for publishing. 

Postprint - peer reviewed but not typeset for publishing. 

In Gold Road Open Access, the article is published in an Open Access journal, which is available for free on the web and allows copies of the article to be archived elsewhere as well. 

Open Access journals do not charge readers or libraries, but their economic model relies on author fees. In other words, the author of the article pays to have the article published in the journal.

Some Green Road Open Access journals charge per manuscript published, and some charge per manuscript submitted.

The author may receive funding from their institution or research grant to pay the author fees. 

In Platinum Road Open Access, the author publishes the article in an Open Access journal, and that journal does not charge author fees. These journals are typically the ones run by professional associations and nonprofit organizations, and their economic model relies on membership dues and donations. Platinum Road Open Access journals run by government agencies are funded by tax dollars.

Most people still just call this Gold Road without author fees.

In Diamond Road Open Access, the author submits a preprint to a repository. They may also publish the work in a regular scholarly journal, and if so, they must retain their copyright just like in Green Road Open Access.

What makes Diamond Road different from Green Road is that the preprint then becomes part of an "overlay journal" which is available online for free to readers and libraries. 

Because preprints are not peer reviewed, the overlay journal must have its own system of quality control. Some have an editorial review board while others use peer reviewers. How these systems are funded varies from journal to journal, and may include membership dues and donations. 

Diamond Road Open Access offers the possibility of a new and different vehicle for scholarly peer review and publication based on voluntarism and the Sharing Economy. Some scholars believe that, due to rapid inflation of prices concurrent with the diminishment of academic library budgets, conventional journal publishing is an unsustainable business model. Some of them do not expect that Gold Road (author pays) Open Access will be any more viable as the sole alternative. They support the development of a sharing economy-based system for peer reviewed scholarly communication to operate as a shadow economy and possible successor economy. 

Most people still just call this Green Road, because the "overlay journals" haven't taken hold as a concept yet.