it's a change in the language file.
/language/en-GB/en-GB.com_dtregister.ini
Line 729 DT_MODERATOR="Moderator"
I am using an older version (2.8.2a) and so the actual line number might be different, but the line you want to change may be approximately line 729.
Change the "Moderator" in quotes to whatever you want it to say-- leave the rest of the text intact. Everytime you install an update in dtregister you will need to going in and update your language file again.