Green open access refers to self-archiving of a pre-print or post-print article in an online repository. In this model, an author publishes in a traditional closed-access journal but reserves the right to distribute the content of their work in an open manner. US copyright law states that distribution of intellectual property is the sole right of the copyright holder, and so in negotiating with publishers, where contracts often strip authors of their copyright entirely, it is crucial that authors either explicitly retain this right, or have the explicit permission of the publisher. This is the model that Open Access Policies are designed to support.
SHERPA RoMEO is an online resource that aggregates and analyses publisher open access policies from around the world and provides summaries of self-archiving permissions and conditions of rights given to authors on a journal-by-journal basis.
It's important to note that a social networking site is not an open access repository:
Remember that with any 'free' for-profit online service, you are the product. When looking for a repository you want to find one that:
This is why funders do not recognize Academia.edu and ResearchGate as fulfilling their open access requirements.
Academic libraries are often involved in the creation and management of institutional repositories that focus on preserving and disseminating the scholarship produced by their institution’s faculty and students.
Disciplinary repositories perform the same sorts of services as institutional repositories, but for scholars within particular disciplines or groups of disciplines. Examples include:
Gold open access refers to articles in fully accessible OA journals. Publishing costs money, and while traditionally that money has come from subscriptions - a 'reader pays' model - gold OA is an effort to explore the alternatives. One popular model is an 'author pays' system, where publishing costs are supported by article processing charges (APCs) paid by the author. But this is not the only possible method, and there are funders and academic societies experimenting with ways to cover costs outside of the for-profit publishing system that do not put a burden on authors.
Some closed-access journals offer the option for authors to make individual articles open access (freely available to everyone) by paying an APC fee. Most OA advocates are suspicious of this model, as it seems to offer the opportunity for publishers to 'double dip': the author pays the APC fee, but libraries must still pay the full subscription fee for access to the journal as a whole, without any kind of discount for the issues that include hybrid-OA articles.