Will Adobe Fontfolio 9.0 work on MacOSX Yosemite?

The Adobe Font Folio product is not an executable program, but rather, for the most part, a collection of fonts. As such, it is not as OS-dependent as most other Adobe products are. I will also assume you are referring to MacOS 10.10.

Font Folio 9 at this point was released over 14 years ago, at the beginning of Adobe's switch from issuing fonts in Type 1 format to the new OpenType CFF format. Relatively few of the fonts in Font Folio 9 are in OpenType CFF format. Most are in Type 1 format.

Adobe applications such as Illustrator, InDesign, Photoshop, and Acrobat still fully support Type 1 fonts, but you should be aware that support for Type 1 fonts in recent MacOS versions is at best waning. Even for Adobe applications, we would not recommend starting new projects with the older fonts due to workflow issues and the lack of support within those fonts for many typographical features available in those applications.

Thus, there is a big difference between whether you can use Font Folio 9 and its fonts versus whether you should use it!

          - Dov