King's Quest V's floppy version had that rune spell copyright thing that was more annoying than anything, but the CD version leaves that out, mercifully. King's Quest III and VI have copyright protection in the form of lore and spells which, IMO, are actually fun to engage with and I wouldn't cut them out even if I could.

The forth game, however, has that rather annoying "what's the Xth word on page x?" that's just tedious to bother with every time I start the game. Does anyone know of a hack of some kind that disables this particular screen and skips right to it? I believe ScummVM already does so, but for accuracy's sake I'd prefer to play in DOS if I could manage it.

I found two solutions for this.

https://www.adventuregamestudio.co.uk/site/games/game/2533-king-s-quest-iv-the-perils-of-rosella-retold/

One is a point and click remake of the game. It's not as drastic as the VGA remakes we've seen of 1-3, but it's still well done.

The second if you prefer the parser interface is:
https://community.pcgamingwiki.com/files/file/1746-ultimate-kings-quest-4-patch/

This patch. This patches the original KQIV's files with numerous fixes, including MT32 sound turned on by default, the Amiga sound effects, the complete artwork from an earlier version of the game, and yes, it disables the copyright protection screen at the start. It does everything except add in the developer room easter egg and the item descriptions from the AGI version.

For ScummVM always remember that you can load saved games from the ScummVM GUI.
Normally you can't do that with original SCI, but with ScummVM you can.

And thus you only have to solve these copy protections once.

ScummVM does not remove any copy protection, unless there is an official release of the game with the copy protection disabled THROUGH THE ORIGINAL INTERPRETER. I don't think that Sierra ever disabled copy protections for their games especially not through the interpreter. They removed some for re-releases, like King's Quest 5 on CD, but that's another story.

The former actually happened for certain LucasArts games if I remember correctly. Please always remember that you should not use fan made patches when playing through ScummVM, because these should not be needed and can cause issues down the line.

ScummVM tries its best to patch games on-the-fly internally and remove all sorts of known bugs from games.
The SCI engine within ScummVM also doesn't have all sorts of issues that the original SCI interpreter has, and thus all sorts of bug fixes are not even needed, and fan patches can instead cause harm.

If there is a game bug that is not fixed by ScummVM, please better report such bug to the official bug tracker so that it can be fixed this way. The patching within ScummVM works in a dynamic way, so that different versions of the game are supported as well as localized versions and all will be fixed at once. You can't apply fan made patches to different versions/localized versions most of the time, because the game scripts will be incompatible.

Certain fan patches also make saved games incompatible. So if you play the game up to a point, then apply fan patches or remove them, and try to restore the game, it may not work anymore. This applies to both the original DOS interpreter as well as ScummVM. I planned to change the saved game code so that saved games would not be affected by fan patch removal anymore, but I wasn't able to finish that work yet.

I didn't mention ScummVM once. This has nothing to do with them. One of these patches is played through DOSBOX, and the other is it's own distinct executable.

As an aside, I find it very frustrating that GOG has removed the old DOS executable from these games. It's entirely fine if they decide to switch the default launcher for these games to SCUMMVM, but deleting the executables serves no purpose at all. They barely occupy any space at all even on the original floppy they came on. Just leave them be. As it stands I had to go and fetch the executables from my old KQ collection discs and re-insert them in the appropriate folders.