Here's another question I get very often...
Is there a SIP firmware available for the Nortel i2002/i2004 phone?
Unfortunately there isn't (and won't be) a SIP firmware for the Nortel i2001/i2002/i2004 IP telephone. If you are interested in connecting one of these handsets to a Asterisk call server there is a UNIStim module for Asterisk that will allow you to use the above mentioned handsets.
Good Luck!