I'm not versed enough in WebLogic to give you a direct terminology map, but I believe GlassFish provides what you're looking for. GF follows a domain model as well with each domain being administered by a Domain Administration Server (DAS, which itself is a full JEE server instance). Each OS you deploy to (whether it be across physical hardware or VMs) gets a Node Agent (NA) which controls communication between the DAS and the Server instances. At that point, you can install any number of server instances that are administered from your original DAS. Further, these can be stand alone instances or you can cluster them for things like high availability, configuration consistency, rolling upgrades, etc.
A good overview is provided here:
http://docs.sun.com/app/docs/doc/820-4342/abfay?a=view
As long as you track your ports to keep from overlapping, you can also install multiple DAS instances and then multiple server instances in the various domains you created.
Chris
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