Did you really follow http://openacs.org/projects/dotlrn/dotlrn-doc/dotlrn-installation, especially the paragraph where it says:
If you are installing OpenACS, follow the extensive installation documentation. Stop at the point where the OpenACS installation instructions tell you to "download OpenACS". Don't use the "Quick Downloads"! Continue on with this document.
cvs -d :pserver:email@example.com:/cvsroot login
(just hit return for the password)
cvs -z3 -d :pserver:firstname.lastname@example.org:/cvsroot checkout acs-core
Also have a look at the comment at the bottom of the installation instructions.