I have put an updated version of the install instructions to
https://openacs.org/xowiki/pages/en/xotcl-core
I removed that part describing libthread from the mentioned
README-file; libthread is not required for xotcl-core and xowiki.
As Rodrigo mentioned, the ajax-chat is a copy of the xowiki ajax chat; i would actually recommend to install xotcl-core and xowiki and use the ajax-chat from there, since when i make some updates there, they won't show up in the copy in dotlrn-chat. A few days ago, i fixed e.g. a problem with UTF-8 characters.