The ethics and idealistic rhetoric aside, there are some practical considerations. Namely that of technology changing much faster than the current copyright scheme. I am not talking even about music or outdated business models or anything like that.
Even though technology changes rapidly, MoO2 is on a platform that has generally maintained backwards compatibility - and there's even software that could emulate the platform as well. Such compatibility removes all practical limitations, and will keep it that way for a while.
Compare this to old NES games or arcade games, where the hardware platform gradually gets rarer due to lack of production and cartridges gradually decay. As time progresses, it becomes harder to play those games - unless you can find an alternate means (which requires violating copyright unless you have your own hardware to extract data from the cartridge.)
If there's no practical issues, this leaves only ethical issues concerning copyright.
So I would ask that Duke Nukem idiot, to go connect to TEN, and I challenge him to a game of Duke Nukem 3D, or if he can connect to my computer VIA his 2400 baud modem and beat me in a game we will all accept what he says as Gospel.
In case of Duke Nukem 3D - original multiplayer is prone to sync issues. The soruce to that game is also released, allowing you to make your own multiplayer system that works across the internet. (Currently, EDuke32 handles multiplayer.)
P.S. Someone jokingly mentioned a unit of time for Public Domain being a DukeNukem which would translate to 15 orbits of our sun,
I'm more of a fan of ~30-40 years. That way, a person born when Duke Nukem was released would have attended sufficient school in order to release their own equivalent (which they can, due to release of tools such as Unity, etc.)