As far as I know, you are the only person to have ported one of Deadlock989's original mods to 2.0. Does this comply with the original license? Naively, I would think that your mod is just a change in format, but you've also added compatibility for belts from other mods, which would make it more of a derivative.

Don't worry, I'm not going after you. Rather the opposite, I have a special project in the works and I would appreciate your input on the matter.

Hello, thanks for asking. Deadlock989's licensing is the elephant in the room after all, since it's the most restrictive CC license.

Does this comply with the original license? [CC BY-NC-ND 4.0]

I must admit it does not fully comply with the CC BY-NC-ND 4.0 license. But only regarding the "No Derivatives" part.
Like you pointed out, the compatibility options for other mods (+ other extra bits of code or sprites) make it more than a simple change in format.
Even my original "2.0.0" release adds derivative content (changes in the code beyond porting, custom sprites to fit turbo belts).

Regarding the other aspects:

• "Attribution": I do credit Deadlock989 explicitely in the description and link both the original 1.1 mod and the licensing page in my mod's page. I do not claim to have created anything before my changes.
• "NonCommercial": I'm not making any money off of this, nor am I using it as advertisement. I mostly made this freely and for fun.

Technically, this mod is a derivative and should not be distributed publicly like this.
I'm doing this out of genuine appreciation for his work and because I want people to enjoy it too.
If he ever contacts me about this mod, I'll comply with his demands and take down the mod if he so asks. (and perhaps reupload a compliant port)

Don't worry, I'm not going after you. Rather the opposite, I have a special project in the works and I would appreciate your input on the matter.

I see. I believe as long as you credit Deadlock989 fairly and only do minimal changes to the mod (to adapt its code to 2.0), everything should be fine.

I'd love to see your project come to fruition! IR3 is very dear to me (so much so I've taken the time to fully translate it and all its addons in my native tongue...) and I'd be glad to help if I have time.

You might also want to hit up 0n0w1c. They've been uploading patches to retexture factorio machines into IR3 ones. Unlike me, they're only instructing users on how to get the original IR3 asset files and patch them in by themselves, not redistributing modified assets.
This method is undeniably fully compliant with the CC BY-NC-ND 4.0 license, but it's unpractical for the average user.
(EDIT: Nevermind, looks like you've found them already :P)

Good news, it is now on the portal. It does require "assembly" like 0n0w1c's mods.

The reason I've taken this approach is because during my background research, it would seem that Deadlock has been somewhat unkind towards other people re-uploading his projects in the past. I have put far too much work into the project for it to be taken down on a whim.

Very well! It's entirely fair to go for that tbh. "My" mod is comparatively very small so I'll take the risk.
I'll try your IR3 patchset once I get into a factorio phase again. :)

Maybe later you could patch in the various IR3 addons as well?
Stuff like Powered Loaders/Stackers or the Airships. (EDIT: Nevermind, looks like you already did :P)
You could also patch in some trigger techs based on Inspiration. It depends on your plans for the future I guess.