26 minutes ago, Zorberson27 said:

The company doesn't even exist anymore and no one owns them.

I'm afraid @DarkRonin is correct, that's not really how intellectual property rights work.  It can sometimes be very hard to figure out who, but unless they were explicitly waived someone will still own those rights.  Typically when a business owning property rights is shut down, the rights are liquidated and sold off to other businesses who may or may not actively use them.

Unfortunately, that means we can't allow this particular discussion here unless you can demonstrate that the rights have been waived or the properties released into the public domain (or provided under some permissive license).  Reverse engineering is (perhaps unfortunately in some cases) illegal in some jurisdictions, and many of our members make a living producing digital products, so the community tends not to take kindly to property rights not being respected.

Please don't discuss copyright law in a game development forum. That being said, I'm not sure anything in the original post request is particularly related to copyright. In fact, I don't even see a clear question in the post -- what technical question do you want an answer to?

That being said, network protocols are often not covered by copyright, and only seldom covered by patent rights, so discussion about network protocols is alright as far as I can tell. There is also the DMCA for those who work in the US, where reverse engineering might be restricted if it's specifically for a DRM technology, so that might be something to watch out for.

For the separate question of "could I distribute versions of this client?" that's a two part question, as in "would it be technically legal" (which you should ask a lawyer about) and "would I get caught and what would happen if I was?" which you'd have to figure out for yourself. (Hint: a game development website is not the best place to figure this out.)

It may be that the best way to revive that client is to build a separate DLL that implements the DirectPlay8 interface, and make it do whatever you need to do in the functions used by the program, rather than trying to 

Now, if you want to create an actual business, you're probably much better off just re-building whatever it was that you liked about this game in a modern framework, and ship it. Ideally, on mobile, too, which is a bigger market than PC, and these kinds of games always want as big a network effect as possible. But if it's just for education and research, try injecting yourself as a DLL and see where that goes.