This package includes all the ObjectMemory/Interpreter classes, the VMMaker/Tool classes, the InterpreterPlugin hierarchy and all the assorted helper methods. It does not include the handwritten platform specific C code that you will also need. See the documentation for the specific release for more details.
If you install this you will be able to build or simulate a VM or plugin - as long as you have the platform sources tree from our SubVersion server
See http://wiki.squeak.org/squeak/VMMaker for more details on the design and operation of VMMaker