I got further in the upgrade, now I need some help from someone else. The following packages are not available in OpenACS 5.1 anymore:
/acs-content/
/acs-util/
/acs-workflow/
/irc-logger/
/viewcvs/
If someone has the time to at least port irc-logger and viewcvs from the current code of openacs.org to be suiteable for and useable in OpenACS 5.1, that would be great.