Hi there,
first of all: thanks a lot for open sourcing BitKeeper!
Your documentation on https://www.bitkeeper.org/install.html#_building_from_source contains an incorrect filename:
$ curl http://www.bitkeeper.org/downloads/latest/bk-7.2.1ce.tar.gz | tar xfz -
It should be:
$ curl http://www.bitkeeper.org/downloads/latest/bk-7.2.1ce.src.tar.gz | tar xfz -