Messenger Plus! Live contains no viruses, trojans, spyware etc. The sponsor program however contains some adware. Nothing serious just a few pop ups while you are browsing the internet etc.. Having this helps keep MP!L free. The sponsor program is completely optional. You do not have to install it if you don't want (which I am guessing you don't want it). Just click the second option in the installer and no adware will be installed on your computer. If you have accidentally installed it, it is very simple to remove and you can find more information about removing the sponsor program in this
thread.