I have activate SNMP and followed these guides :
http://www.observium.org/docs/unix_agent/
http://www.observium.org/docs/distro_script/
http://www.observium.org/docs/apps/

But, Apps tab is not display after discovery/poller.
In the old Observium version, the Apps tab is show after poller for the same server.
In attachment the poller with -dd and -m unix-agent options.
You can see the unix-agent module is activate and Apache & Mysql is present.