It was taken down. In general, 18F’s open source work was in the public domain, though, and I know there have been efforts to archive it recently.

Additionally, it looks like some of 18F’s public guides are still available (e.g. the “Derisking” guide, which is all about how to structure your IT projects to be less likely to fail spectacularly: https://guides.18f.gov/derisking/)

Yes they tore it down.