As some other plug-ins may use this way of doing and you don’t want it, you could try to set the user.name property to another value with the Java option [font=courier new]-Duser.name=myname[/font] (this option can be set using the same way as the -Xmx option used to increase memory and explained in the FAQ).
This should fix this way of doing that you consider as a security leak.

That works! (Although I'm still of the opinion that it's a serious security leak that should not have been introduced in the first place.)

I also found a second way around this which might be usefull for other users: Use the furniture library editor for every single object you create where you can set the creator name for each object. Once you add furniture in your plan that is imported through a furniture library the name is used as set in the library. This also allowes to use multiple different creator names if you wish to do so.