Unless there is a move away from GPL, I don't think it's worthwhile to split hairs on all these intricacies. What is discouraging users is "GPL" and I don't think adding more exceptions will avoid the negative perception. If Massimo is married to GPL then there's probably not much to discuss.
I don't buy that Massimo doesn't care about the number of users. He promotes the heck out of Web2py. And frameworks benefit greatly from usage. I also don't understand how GPL helps to "create a good framework". Does BSD/MIT somehow prevent that?