VFlib is distributed by the form of source code.
You must compile it and install by yourself. Read a guide for installation.
It optionally requires FreeType 1.2 or later, T1Lib 5.1 or later, and web2c 7.2 packages as external libraries. Download and install them before installing VFlib 3.
TeX-Guy is a set of a device independent TeX DVI interpreter and previewers and printer drivers. It uses VFlib 3.6 as a font module. For further information on TeX-Guy, see the Web page of TeX-Guy Project.
To install VFlib 3, following libraries are (optionally) required. Install them before you compile VFlib 3. These external libraries are optional and therefore VFlib 3 can be compiled not to use such libraries. But in such a case, you cannot use TrueType, Type1 fonts and searching TeX fonts is very limited. So, I strongly recommend to use such libraries. See install guide for VFlib3 for detailed information for external libraries.
VFlib 2.25 requires FreeType 1.2 or later. package as an external library. Download them and install before installing VFlib 2.25.