Main guy at oldunreal has an NDA for UE1. he has source code for versions..
220, 224v,(225f was lost/overwritten by 226f) 226f, 400, 432, 436, 451 and some unreleased builds of UT. upak.dll source was never dug up by epic -- "we dont have the bandwidth to..." so it's just a dummy dll where the original intent of the code was rewritten in uscript.
For what its worth, when Tim says the middleware in UE1 is a problem -- it's not. Galaxy source code was given to the devs from the original creator, and all renderers and such were made by the community. This also includes some new audio drivers.
Best I can think of that might be blocking is some proprietary intel SSE/gamespy shit still in the source code. Intel SSE instructions have C++ equivalent code -- so they can be stripped easily.
also, UE1 is surprisingly similar to UE4. More or less UE4 has a better rendering system, better audio system, and less... hacked physics/actors. The core workings of the engine (actors, subsystems) are largely the same.UE4 still has unrealscript, it's blueprints now, there is no uscript compiler as /vr/ knows it, but you could theoretically reimplement it if you had UnCorSc.cpp