Yes, it is real. It is called Fallout Equestria: Remains, and it is Bloody Amazing™. And I don't get why so seemingly few people know of its existence.

The deviantart page is here.
The newest version (as of the time of writing this) can be found here.
And the wiki is here.
And there are also some screenshots on Derpibooru.

Please, check it out, and spread the word if you can. This game deserves every piece of attention it can get!