This piece of 'spyware' is in fact Adware that was installed during the installation of plus... for removal instructions please go to this website:
www.mpsupport.net or this thread:
Messenger Plus! Sponsor Removal Instructions
If you want to know about the sponsor program then:
Basically, the sponsor program was added to Messenger Plus! so that Patchou could have an income, as Patchou is working constantly on this Extension to make it grow, and it trully has, so while Patchou is working on this, people are accepting the sponsor software, therefore, patchou is earning a minute income... It is there for Patchou's sake...
It isn't spyware, it is adware from c2media, but with their permission, Patchou has stripped it down to a bare minimum so that people's computers aren't ruined, it is a small sponsor program...
It is completely optional and when you get to:
that screen, you simply press, I refuse...