I did some compatibility tests with freePBX 2.2/asterisk 1.4 and works quite well.
Followings, some little modifications to make it works.
In sip.conf for example i added this to enable BLF of my phones and jitterbuffer:
notifyringing=yes
notifyhold=yes
limitonpeers=yes
jbenable = yes
jbforce=yes
and in sip section of core functions.php
$tmparr['call-limit'] = array('value' => '4', 'level' => 1);
In functions.php of queue module, change all "$CALLERIDNAME" (also obsolete for asterisk 1.2) to "${CALLERID(name)}".
In functions.php of meetme module, change line 18 from:
$output .= 'conf => '.$meetme."|".$this->_meetmes[$meetme]."\n";
to
$output .= 'conf => '.$meetme.",".$this->_meetmes[$meetme]."\n";