While several people have told you already that the password isn't going to get you anything... I'll put it in computer guy terms (since I am a computer guy).
The web interface is useless and no effort should be wasted here, there is zero information here nor any config at all.
Neither will any serial port yield you an interface that is anything but a low-level debug monitor or set the basic bootstrap settings (ie. IP address to talk on the Network).
The *only* way to program/backup/do anything with an inter-tel system is with the proprietary inter-tel software running on a PC, and connecting over serial or an IP connection (or dialin modem).
This software is extremely version dependent (ie. you need the software for that exact version of code you are running). It is only available to Inter-Tel/Mitel dealers/techs (or very unofficial channels).
This software is the only way to backup or change a configuration.
This situation is pretty typical in the telephone equipment realm. Ie. Panasonic KSUs need their proprietary software (although most Panasonic systems being pretty fixed in config would default to a system that is close to what most companies using it would have setup anyway). Avaya is very proprietary software as well depending on hardware and config.
