Maybe the $AOLHOME/servers/servername/modules/tcl directory did not get copied
Thanks. That was the clue I needed. The config file for the original server is in /usr/local/aolserver. In setting up the copy, I put the config file in /web/devel/etc, more in line with the current installation instructions, and that was causing the problem, because my config file (which has been around for a while) set $homedir like so:
set homedir [file dirname [ns_info config]]
So this caused it so look for /web/devel/etc/modules/tcl. Moving the config file to /usr/local/aolserver fixed it as did just setting $homedir to /usr/local/aolserver, like the current reference config
