Attached is a patch that makes suites.All pass both with and without derbynet.jar in my environment. It makes the following changes:
The test cases in this class require the network server, so I made the suite() method return an empty suite if the server isn't available.
This class couldn't be loaded by derbynet._Suite because of some local variables of type NetworkServerControl (which is a class in derbynet.jar). Not sure exactly why this caused a problem, as other test classes have local variables of that type and can still be loaded. In any case, the class loaded just fine when I changed it to use some helper methods in NetworkServerTestSetup to access NetworkServerControl.
One of the test cases starts an external network server. I made suite() skip that test case when the server classes are not available.
The ReplicationRun class uses NetworkServerControl in some of its method signatures and cannot be loaded if derbynet.jar isn't on the classpath. I made ReplicationSuite return an empty suite if there is no network server, so that it doesn't try to load the ReplicationRun class.