Fun Fact:

Van Buren is the codename Black Isle Studios assigned to their second iteration of Fallout 3. It saw development by Black Isle Studios until its cancelation in December 8, 2003 and would have been published by Interplay Entertainment.

https://fallout.fandom.com/wiki/Van_Buren

The design documents were later leaked and it seems like Fallout New Vegas took heavy inspiration from them. Retcon Raider created a video series going through the documents you can view here.

With the background out of the way (TL:DR) there have been several attempts to recreate what Van Buren would have been and some of them did end up using FOnline Engine initially before switching to Fallout 2's engine.

By the looks of their Patreon page Fallout: Yesterday is still being developed.

That said the video was interested. I know there were a few FOnline games back in the day but I am curious which ones are still active. I believe I used FOnline Reloaded

Edit: Apparently Warlockracy also did a video on Fallout Yesterday you can find here.