On AIX, by default the named program is linked to named8.
michael@x054:[/usr/sbin]ls -l named*
lrwxrwxrwx 1 root system 16 Oct 01 21:00 named -> /usr/sbin/named8
lrwxrwxrwx 1 root system 21 Oct 01 21:00 named-xfer -> /usr/sbin/named8-xfer
-r-sr-xr-- 1 root system 652686 Feb 08 2007 named8
-r-xr-xr-- 1 root system 185628 Feb 08 2007 named8-xfer
-r-sr-xr-- 1 root system 483964 Feb 08 2007 named9
I am not sure about where you can find version information. Maybe if you setup the syslog system (e.g. daemon.info /tmp/daemon.info files 5 100k replace) you could start the named system and see the version in the startup string.