Julian Seward lost the Bzip domain to squatters in 2018. Confer, https://sourceforge.net/p/valgrind/mailman/message/36403434 .
The new site for Bzip2 is located at Sourceware hosted by Red Hat. Sourceware are the folks who maintain Linux Binutils, GDB, Glibc and friends. The Bzip2 site is now located at https://sourceware.org/bzip2/ .
The sourceware project isn't new. It is old before the original bzip.org site and it's latest version is 1.0.2. This project was created in order to have an active place for the current library and I used SorceForge because the bzip.org site points to SourceForge for the download. Neustradamus is working on moving the active development to github.