[Freeswitch-users] MPL in simple terms

Is there a simple explanation, in terms that a mere software engineer can understand, what the MPL license means? 1) Can I sell FS under my own guarantee and support? 2) If I write code that connects FS to an external application that I have written, does the external application have to be MPL as well? 3) Extension to previous question: What if the external application is Active Directory? Thanks, Simon