From the legal point of view the answer is yes. Mibew Messenger can be used as a base for SaaS. But you'd better consult with a lawyer in your country, 'cause there could be a dozen of rules and regulations.
From the technical point of view. Well, I can give you one simple hint: hire a programmer or two.
And the common part. You've come to our public forum and ask us how to make money on our software. Given the fact that you've done nothing for the project that's just gorgeous plan.