In my case I want to write an app which is totally symetrical (not client-server) with identical functionality at two PCs, one a 'standard' Windows or Linxu box and the other an Android slate.
Can I run the same program on both or do I nneed to wrap it in an Android package for persmissioons, etc?
The two PCs will communciate by TCP/IP, sort of peer-to-peer, but I suspect that as a generic question this might be of interest to many.
Well you cannot run an independent java application on Android. Android applications are compiled to dalvik bytecode and really are just written in java but not run on the java vm (Android does not have a java vm). However you can create a jar library that can be consumed by both a desktop and android application and that should provide reuse of platform independent code.
You can run command-line Java programs on an Android device. An example of a simple "hello, world" program is described here.
As noted previously, though, you can't use the Android framework for UI, and unless you have a rooted phone you won't be able to install it in /data or access "protected" features like talking to the Internet.