I built a simple social community website for a client - the client would like to add in a forum and he likes Simple Machines Forum. The website I built has its own users management system. The client would like SMF on his website and at the same time when a user is logged into the website they don't need to log into SMF website as well... how can this be done? Or should I just tell the client to consider two separet independant applications in this case i.e forum totally disjoint from the main site?
SMF has an API available and there are bridges for several popular CMS on the SMF site.
You would have to build a bridge for your community site or use an existing one if your site's CMS already has one.