It should be easy to copy the standalone dir to another dir (say, "serverB" in the same level in the FS tree) and launch a second server using ./standalone.sh -Djboss.server.base.dir=serverB
It somewhat works, but things that aren't as smooth as they should be:
a) The resolution of jboss.server.base.dir isn't very smart. For example, to do the common thing and launch the script from within the bin dir you have to either use an absolute path to instance1/2 or do something kludgey like:
If the path is relative and resolving it doesn't result in a file that exists, an attempt should be made to resolve against jboss.home.dir.
2) The launch script directly references the standalone/configuration/logging.properties and standalone/log/boot.log files. So, if those files aren't present the server doesn't boot properly, and both, e.g. serverA and serverB will use the standalone/log/boot.log as their boot log file (where logging goes until the boot process starts the logging subsystem.)