OA journals provide free access to their articles but may charge the authors a publication fee called the "article processing charge" (APC). DOAJ (Directory of Open Access Journals) provides a list of OA journals that exercise peer-review or editorial control and also their article processing charges.
The author of the publication will need to absorb the cost with a research grant (if any) if there is no sponsorship from the author's department.
Most publishers specify on their website the versions of the work they allow researchers to deposit in an institutional repository for OA*. The permitted versions are:
also known as Early version, Submitted or First manuscript. Usually in word processing format, this is the version an author submits to a journal for consideration before the peer-review process.
also known as Accepted Author Manuscript, Peer-reviewed or Author Final version. Usually in word processing format, it contains all the revisions made during the peer-review process.
also known as Publisher's PDF, Publisher's Final version or Version of record. It has the final layout and formatting done by the publisher for the purpose of publication either in hardcopy or electronic format.
SHERPA/RoMEO publisher policy index provides information on the copyright and self-archiving policies of publishers.
*Usually publishers allow authors to post copies of pre-print or post-print rather than the final published version for OA archiving.
An embargo period is a period of time following the publication date of an article or journal when free access to the full text is not available. This period of time varies depending on the policies of the publishers. Access to the full text during an embargo period is restricted to users who have paid a subscription.
The copyright transfer agreement (CTA) or the publisher's agreement is a legal document that states the condition of publication which can be a full or partial copyright transfer or a license to publish. The author who creates the work is the copyright holder. Copyright is a bundle of rights. The CTA may specify various rights that the author does retain, such as whether the author can post the article in an open access repository and under which conditions. If the CTA does not specify what rights the author can retain, the author may have transferred the whole copyright of his or her work to the publisher and thus will need to seek the publisher's permission when using part or whole of the document unless the use is one of the statutory exemptions in the copyright law.