The project you linked does have history, it wasn't written from scratch just recently, it actually dates back to 1996, if Wikipedia is correct.
Not exactly new neither, but the guys that maintain Myth II these days also kept support for Windows 98 at least. I haven't tried Win95, it's likely that it works as well.
What's also interesting, the engine may render using old Direct3D (libraries from Direct3D 7 and earlier era), Glide2 (3Dfx API), OpenGL and even Direct3D 11 library (d3d11.dll), in the latter case, it may not actually utilize the newest features (you can still target Direct3D 9 level hardware with it).
Maybe I forgot some API in between as I'm not on the computer with Myth II installation ATM.
Edit: Added screen of the preferences screen. Rendering listbox only shows what's available, so 3Dfx Banshee SLI will only appear on modern machine if you have glide2x.dll from one of the Glide wrappers installed (eg. nGlide, dgVoodoo).