For my purposes, a journal is open-access if and only if it is free to write in and free (or negligibly expensive) for anyone with an Internet connection to read. Journals which charge $1000 or more for the privilege of hosting a PDF edited by the author and unpaid volunteers are not open access by this definition. A venue is active if and only if it still accepts new publications. Many out-of-print monographs and back issues of journals have been made open access, but this does not help when you are looking for a place to publish your new research as opposed to trying to obtain old research.
- Greek, Roman, and Byzantine Studies https://grbs.library.duke.edu/index
- Acta Periodica Duellatorum https://bop.unibe.ch/apd
- Ancient History Bulletin (articles cost about $1 each)
- ARTA: Achaemenid Research on Texts and Archaeology http://www.achemenet.com/en/tree/?/on-line-publications/arta
- Gladius gladius.revistas.csic.es/index.php/
- IBAES: Internet-Beiträge zur Ägyptologie und Sudanarchäologie http://www2.rz.hu-berlin.de/nilus/net-publications/ibaes.html
- Journal of Ancient Near Eastern History https://www.degruyter.com/journal/key/JANEH/html
- NABU: Nouvelles Assyriologiques Brèves et Utilitaires https://sepoa.fr/
For books, I also consider publishers which charge a fee in the low thousands and make the PDF but not the print version free to read.
- Access Archaeology (Archaeopress) https://archaeopress.com/ArchaeopressShop/Public/defaultAll.asp?displayPage=Publish+in+Access+Archaeology
- Zea E-Books, University of Nebraska Press https://digitalcommons.unl.edu/zea/
- AWOL List of Open Access Journals in Ancient Studies
- AWOL Active Open Access Journals in Ancient Studies
- AWOL Alphabetical List of Open Access Monograph Series in Ancient Studies