Question about Speech-dispatcher

[Hermann]

I had to compile SD from the source for my Ubuntu laptop, because SD 
0.6.3tested always crashs when an updatedb was performed in the background.
Getting the packages from the Hardy branch was not possible, because 
dpkg indicated, that various core packages were missing.
I succeeded in building and setting up SD 0.6.6, although it was a lot 
of work.
But one question remains: I had to add a user "speech-dispatcher" to my 
system by using the adduser command. This adds a regular user with 
password, homedir and all privileges of a common user.
I think this isn't necessary for SD, but I don't know how to add a user 
with less privileges, a kind of shadow user that only exists by name.
Is this possible, and if so, how can I perform this?
Hermann