Asterisk is a server-based VoIP phone system that is usually run on Linux, and usually run on a network. I have seen posts for Asterisk on Server Fault, Stack Overflow, and Super User. I even saw one post somewhere in those sites (sorry, I can't remember where and cannot find it in my history) where there was a debate about whether the user's Asterisk question ought to be posted in Super User or Server Fault.
What is Asterisk (now deleted) is an Asterisk question migrated from Super User to Server Fault.
Here (now deleted) is a comment on Stack Overflow, by a rep of 635 where the user was told his/her question would be better asked on Super User or Server Fault.
Hence, what is the most relevant Q&A site for this, Server Fault, Stack Overflow, or Super User?