The back end for OASIS is Tamino; finding aids are displayed ion a frames-oriented template in HTML. They can be printed from PDFs made available on the OASIS website.
OASIS is a project involving 22 Harvard repositories. With so many participating institutions, the procedure used for EAD markup is slightly different at each, although all follow the established Harvard guidelines (available at: http://hul.harvard.edu/ois/systems/oasis/eadguide.html ).
The legacy finding aids in OASIS were created using various word-processors; they have been converted to XML documents by a variety of manual and partially-automated methods, or by outside vendors. New EAD finding aids are being created in XML, using a variety of applications including WordPerfect and XMetaL.