In order to remain current, each Eclipse release targets reasonably current versions of the underlying operating environments. The EMF Compare project depends upon on the Platform,which is mostly "pure" Java™. The 4.5 release of the Eclipse Platform Project is written and compiled against version 1.7 of the Java™ Platform APIs, and targeted to run on version 1.7 of the Java™ Runtime Environment, Standard Edition.
Due to this dependency, EMF Compare when used as part of the eclipse environment will also require version 1.7 or higher of the Java™ Runtime environment to run.
Eclipse Platform SDK 4.4 will be tested and validated on a number of reference platforms.
EMF Compare will be tested and validated against a subset of those listed for the platform.
Given that there is no operating system dependent code in EMF Compare, it's expected that EMF Compare will work anywhere the Eclipse Platform does.