Why would Discourse's business model work when Stack Exchange v1's failed?

[obvio171]

Apparently, yes (bold emphasis mine):

We reserve the right to dabble in advertising if we offer “free” forum hosting, but I’m not sure we will ever do that; I expect the $19-$99 per month small business forum hosting will be the main strategy a year from now. But who knows? A year is a long time away.