Recently, a post by a player under the nickname No_Judgment7651 went viral in the Fallout community. He showed how he launched The Elder Scrolls III: Morrowind on an in-game personal computer "Pip-Boy".
Back then it was a "proof of concept", and now RPGKing117 has presented a full-fledged modification.
The project is based not on the original Morrowind, but on the open-source OpenMW version. From a technical point of view, it is arranged as follows:
The modification streams The Elder Scrolls III: Morrowind in real-time to the "Pip-Boy" screen in Fallout 4, using a specially modified OpenMW 0.50 build — with direct integration into the game engine via shared memory and a separate F4SE plugin. Insert the Morrowind holodisk, open the "Pip-Boy" — the rest is up to you.
OpenMW will run in a hidden window with a resolution of 876×700, which scales to 1024×1024 and will be displayed on the "Pip-Boy" inside Fallout 4.
The "Morrowind - PipBoy Edition" modification is distributed free of charge via Nexus Mods. It requires the Steam version of Morrowind and Fallout 4, as well as the "F4SE — Fallout 4 Script Extender" mod.
Gameplay is available at the following link.