I would stay far away from running an antimalware app with real time file protection on a server.
SBS already has a huge HUGE list of exclusions to use for real time file protection with certified antivirus programs...not to mention trimming down it's file extention types to scan. (do a search on these forums for a long informative thread I have on that topic)
Malwarebytes is more for threats you catch on the web anyways.....no reason for web based threats to be on a server...since, as most IT people know...servers aren't used for surfing the web.