I visited Chapman University's legal library and read through "Intellectual Property Law For Business Lawyers 2009-2010 Edition" to look for how well fair-use defences can work here.
Even if we engage in copyright infringement, courts do judge for fair use against a set of criteria.
I believe that we have a good defence for Finobe, Filtering Disabled, etc.
Self-hosting systems such as Filtering Disabled and Novetus are transformative: they give a new function that the original Rōblox didn't originally have. Can you host a LAN party using 🔒 Byfron-infested Rōblox 🔒? Anything is possible.
Our research is for the betterment of public understanding of how software like Rōblox works. Our reverse-engineering stuffs are in the interest of scientific and social progress. Good.
Marketing revivals can be considered a fair use if they don't adversely affect Rōblox's ability to do commerce. I can argue in a court: people come to Rōblox because they trust the centralised nature of it -- and for the developers which keep the platform afloat.
A lot of people I speak with tell me that they go to Rōblox for a particular game. Maybe it's The Hood. Maybe it's Bloxburg. People buy robux for gamepasses on these games. If these games remain exclusive on Rōblox, the incentive to buy robux doesn't go away.
Courts tend to favour non-commercial ventures over ones which seek to make money, but they will consider other factors equally well. There are many exceptions on either side.
See the decision from Google v. Oracle. Google took a very small portion of Oracle's proprietary source code to make early versions of Android. It was a very small portion and it wasn't at the heart of how Java works. Therefore, what Google did was a fair use -- even though it was commercial.
But...
Courts also rule more in your favour if you're taking a published work. Why? Because if a work is unpublished, that is because Rōblox chose not to publish it.
I think as long as they're newer than 2017, most of the RCC binaries we use require you to know the exact resource locations (URLs) to grab it. These URLs weren't publicly known until we brute-forced our way through all the possible URLs -- I think.
The importance of the parts which we take from Rōblox for our revivals also influences courts' decisions. Rōblox pride themselves on their physics engine. We took that for ourselves. If you're using the 2021E client, you're also taking the complete product of Future Is Bright. Lots of things.
And most importantly:
Most of us entered into a legally-binding contract with Rōblox. If we're reverse-engineering the binaries, we'd be in breach of contract (as per 'terms of service'). Courts don't usually prosecute copyright claims if they rely on a breach of contract (do they?). This is why I think that we'll never have to argue for 'fair use'. I'd probably have other problems first.