Hi all, hi Bernard... probably, my response is a bit late, but I spent time reading (hopefully!) carefully all the answers...
Thus, my 0,02$:
I think that probably the correct question is: "Please convince me to make my business model" :-)
I agree with others that probably, the SaaS business models require closed source. Thus, probably, no choice...
IMHO the open source software implies a different business model, something similar to "partnership".
Good luck, honestly,
Giuseppe Briotti.