Andy (Pneumatic) here on Nicks PC.
There is nothing in the Jetpac code for it to act as a server or open any TCP/IP ports of any kind.
I wonder if there is an aspect of the multiplayer code that gets intialised by another routine in DBPro? I've no answers for you sorry - but Jetpac isn't doing it.
I suggest denying Jetpac connection for your own peace of mind, as net connection really wont make the blindest bit of different to the game.
I've not used zonealarm for some time as I now have a little black box - but perhaps there is something in your zonealarm configuration - maybe 'first run' for all programs?
Pneumatic
Dark Basic Pro drove me to drink, I really should E-mail them to say thanks.