Current support status for the various platforms as well as a web interface for reporting bugs can be found at the SICStus Prolog homepage:
http://www.sicstus.se/
Information about and fixes for bugs that have shown up since the latest release can be found there as well.
The mailing list sicstus-users@sics.se is a mailing list for communication among users and implementors. To subscribe, write a message to sympa@sics.se with the following line in the message body:
subscribe sicstus-users