For my two cents . . .
I would be happy putting the investment my customers make (have made) into RAV into something like CLAM to keep it viable. Given the license the software is developed under then we will never have the MS/RAV situation happen.
So just saying that I for one, as a supporter of SME, and having deployed over 35 RAV for Linux installations (most of which are due or close to renewal) will be happy to (and would rather) put my support behind an open source solution. Maybe we could have one of the project leads from CLAMAV comment in this thread if anyone is familiar with the contacts there?