Open access is a philosophy and not a business model. There are several ways that works can become open access and several ways to pay the costs associated with publication, but there are two main pathways to open access.
Publish in an open access journal
In this pathway, the work is freely available from the moment of publication. This is sometimes called gold open access. There may or may not be an associated article processing charge (APC). Journals that are financially supported by institutions, societies, or dedicated volunteer staff are sometimes called diamond or platinum OA because neither readers nor authors have to pay. Gold OA can also refer to hybrid journals. Hybrid journals are those that still require a subscription to access but that offer authors the option to pay an APC to make their single article open access.
Deposit a copy of the work in a freely available archive
This pathway generally happens either at the time of publication or after publication. This is sometimes called green open access. It typically involves the author, or an author's representative, uploading a copy of the article to a disciplinary repository, an institutional repository, or a personal website.
UT Libraries Support for OA Publishing Initiatives
UT Libraries is interested in supporting a scholarly publishing ecosystem that provides maximum access to high quality information to the greatest number of users. We are also interested in supporting open access business models that are financially sustainable. To that end, we've been supporting several different OA publishing and OA infrastructure initiatives for the last several years.