As the name suggests, all of the Journals we host on Open Journal Systems are indeed open - this means readers can access the content for free after setting up a username in OJS. Please visit PKP's homepage for more information on the explicitly open platform. The software that OJS is licensed under the open sources GPL v2 license.
All of the journals currently hosted by Boston College Libraries use some form of a Creative Commons License that the author signs before submitting the work to the journal for publication. Creative Commons licenses vary in what they cover, but the most common is known as a CC BY license. This means that content that is found on OJS is free to cite and reuse so long as the author is attributed. Creative Commons licenses leave the author as the principal copyright holder, while the library also maintains the rights to distribute published material (or, more specifically, to make sure such content is available.)
For the DOAJ application, you will be asked to describe or provide the language on your journal's Open Access statement. Your eJournal page displays information, like a Copyright Notice - which can be edited in the backend of your website.