I got forums with HTMLarea enabled available but refrain from commiting due to the imminent launches of .LRN 2.1.
As a matter of fact there are only minor changes:
/lib/edit.tcl: set content and format to the same values as in /lib/post.tcl instead of calling the richtext function.
/lib/post.tcl: change all occurances of $format == "html" to $format == "text/html"
/tcl/form-procs.tcl: change the textarea widget to richtext on the message_subject. Add a hidden form element "format" which is set to "text/html".
If someone wants to get the code and play around with it, just ping me.