Sametime and Notes Server

Using Domino 6.5.1 with client 6.5.1 can I have my sametime server and Notes Server on the same server and still not have to purchase additional licenses. From what I have been able to gather, if I don’t want web conferencing and a few other features I already have Sametime client licenses for all my users. And as long as my sametime server is internal only I do not need a license for sametime on the server. I can not figure out if I can have the sametime server that I do not need a license for on the same server I use for Notes or anything else.