Last week, Fallout 3 was finally freed from the scourge of Games for Windows Live. But as is so often the way of things, that freedom came at a price—specifically, that the Fallout Script Extender (FOSE) no longer works, and so all of the many mods that rely on it have also stopped working. Oops. That's a pretty big problem, made worse by the fact that the creators "do not have a timeframe for when FOSE can be updated to this new version" of the game.
Enter the Fallout Anniversary Patcher, by mod maker lStewieAl, which restores FOSE functionality by downgrading Fallout 3 to the pre-update version 18.104.22.168, while maintaining the removal of Games for Windows Live dependences. It also automatically loads FOSE when Fallout 3 is started (if it's installed) and enables the game to use 4GB of RAM: Some older Bethesda games, including Fallout 3, have a 2GB limit on RAM usage, and patching that up to 4GB can have a very positive impact on performance.
The patch will work with both the standard and Game of the Year editions of Fallout 3 on Steam or GOG. Once it's installed you can boot the game however you like—through Steam or GOG, the launcher, or any mod manager—but if you want FOSE to auto-load you'll need to do it with the Fallout3.exe directly, so you'll probably want to create a shortcut. The patcher doesn't include any copyrighted files so you'll need a legitimate copy of Fallout 3 to use it, and it should not be used to install Tale of Two Wastelands 3.2—use this downgrader instead.
It's a bit odd that Fallout 3 would shed GFWL at this very late juncture, although as Shaun speculated when it happened last week, Microsoft's still-relatively-new ownership of Bethesda may have had something to do with it. Whatever the reason, it's good news for fans, who are still playing Fallout 3 in surprising numbers: The average concurrent player count over the past 30 days is 347, which is awfully impressive for a 13-year-old singleplayer RPG with several sequels in the intervening decade-plus.