The 0.9 version of YapBib for Mac was provided as a free download on our website. The program lies within Productivity Tools, more precisely Office Tools.
From the developer:
Yapbib is Your Annotated Personal Bibliography. This program allows you to manage your body of literature research, include annotations per author and per literature-entry, organize and categorize the entries for your specific projects, perform queries on the entries, and export contents on the bibliograpy database in BibTex form. Yapbib uses no external database to keep the software small and manageable.
You may want to check out more Mac applications, such as Synpathy, NeoOficina or T-Styles, which might be related to YapBib.