https://www.reddit.com/r/Fallout/comments/844t22/some_of_the...
At this point I'm fairly convinced that Bethesda is going to announce a 10th anniversary release of Fallout 3 at E3 and don't want the competition.
In fact, working on a mod for a game -- and then getting legally threatened by the owning company of that mod platform -- would entirely drain my enthusiasm or passion for the game/company/platform.
I hope the mod-makers feel similarly.
These conversations can be civil and respectful, even if the outcome is not ideal.
E: Also, some total conversion mods will make a copy of your game installation, then install itself into that copy. I think (it's been a while since I've played them) that Nehrim (Oblivion) and Enderal (Skyrim), both from SureAI, do this.
Bathesda also had some very strange requirements for the OpenMW folks when they were in contact[1]. Namely they didn't want them to show OpenMW working on Android (because Bathesda wanted to port it themselves?) nor did they want them to support the XBox version of the game. I doubt that Bathesda actually had the right to add those requirements to a project that is a from-scratch reimplementation of their game engine, but that's the current status.
[1]: https://wiki.openmw.org/index.php?title=Bethesda_Emails
The rule with these things is typically "If you make us give you an answer about if you can do it, it will be no."
There is a similar project redoing New Vegas in Fallout 4 (F4NV - I'm not affiliated with the project, just a fan snooping on their progress from time to time) and one of the really important things is that they're making their vision of what NV could be. This means all new meshes, textures, and code - not the old content updated to run on the new engine.
I've written some code for fiddling around with the plugins the engine uses (.esp/.esm/.esl files). The basic structure hasn't changed, but a lot of the records and fields have. Automatically converting them well enough to not need manual tidying up would be a pretty arduous task.
Converting the old code into papyrus would be as well.
Then again, I guess releasing your "redo" of some voice actor's soundtrack violates copyright too?
(Like, I couldn't release a set of files of me doing Darth Vader's lines from A New Hope?)