Asterisk and HFA

Does Asterisk support Siemens Optipoint IP Phones with the Siemens propietary protocol or they have to be change to SIP?

They would need to be SIP, H.323, MGCP, SCCP or UNISTIM. These are the channel types supported by Asterisk.

FreePBX is very SIP centric but does accommodate other channel technologies with custom type trunk and extensions.