Thank you for your post.
Your IT person is correct. FileMaker Server should be running by itself.
I do know some customers that have Filemaker Pro Advanced on the same server, but it is only used on a limited basis. If they want to make changes to a file, they close the file in FileMaker Server, open the file with FileMaker Pro Advanced, make the changes, quit FileMaker Pro Advanced, and then return to FileMaker Server and open the file. This is not recommended (as you should copy the closed file to another computer to make the changes), it does appear to work for these couple of customers.