Microsoft CRM Online Licensing question

Ok- Here is another licensing question - 

I work for a government agency in NYC. We are using CRM online for a totalling in house system however we are discussing the idea of adding a public facing front end. I am interested in meeting some enterprise architects who are willing to talk with us about their design to address the portal. 

The concern our Enterprise Architect has raised is that MS will charge us for each citizen who uses the portal. We have some disagreement in house on that idea so we would like to talk to someone who has done it. Our basic design approach is to build a front end in dot net and lets say use dot net forms to capture the customer info. we want to then feed that info into dynamics where we can dashboard the request, report on it, workflow it etc... We even want to give the external customer access to their data. 

Built through a webservice - do i need to license more than one crm license - remember this is for the cloud....

If you could respond great - if you are willing to talk with us - even better... thank you.......