Prebid Server has two code bases: Go and Java. The original version of Prebid Server was the Go-Lang version. Rubicon Project ported it to Java because they had more engineers who knew Java than Go.
Both versions are live in production, and they are kept identical in external APIs and reasonably close in functionality.
For demand partners, we recommend building new bid adapters in Go - the team will port it to Java for you within a couple of months.
For those looking to host a Prebid Server, here’s some guidance on selecting which version to use: