This discussion seems to me to be getting kind of confused. IANAL, but...
First, the EULA doesn't apply any more. Under the EULA, NCSoft's sole legal remedy for violations was kicking you off the service and cancelling your account. That's moot now.
NCSoft still has a copyright in all the source code (moot, because nobody outside of NCSoft has any of it), the compiled client, and all the files that were included with that, most importantly all the art and music assets. If you redistribute the client, then you could be violating their copyright (could because there are a bunch of steps they'd have to go through in court to demonstrate that it was a violation, and there are some affirmative defenses that could be raised). Under the DMCA they could get a service provider (in a jurisdiction that's covered) to take down the client files you were sharing, basically just by alleging a violation... but that's not the same as proving a violation and again there are some defenses against that. Still, they'd be on pretty solid legal footing if they bothered to pursue it.
NCSoft does not have any right to prevent anyone from providing products that are interoperable with their client code, or to prevent reverse engineering their code in order to provide interoperability. This ranges from things like Vidiot Maps to Sentinel+ to a hypothetical server that would respond to messages from the client as if it were the CoX server engine. This is pretty much settled case-law, and there's a particular carve-out in the DMCA specifically to permit reverse engineering. NCSoft forbade it in the EULA (a common tactic to try to skate around the law permitting reverse engineering is to claim that it's nonetheless forbidden by a contract that the company and the reverse engineer have entered into), but the EULA is now moot.
NCSoft still has a trademark in City of Heroes and various names and images (not all of them, but specific ones that served to identify and promote the brand), but that limits what a hypothetical after-market interoperable server could be called and what images it could use to promote itself so as not to cause confusion in the marketplace over whether it's an official product; it does not actually prevent mentioning the trademark for purposes of comparison (10% less phosphates than Tide) or compatibility (usable with iPhone). And that assumes that somebody actually tries to market a product that works with the old City of Heroes clients...which seems unlikely.