I don't think it matters if it works or not...
. It's probably a backdoor trojan, so the 'creator' of the program can also 'hack' your msn...
The 'hacker' needs to give another contact 'a file', before he can 'hack' his contact. I think it promotes itself to the 'contact' as a colored message or something (that's why it should only work with people who have Msgplus installed). Maybe it promotes itself as a plugin. I don't know....
. At least I don't believe that it's something that only affects Msgplus users..