It's precisely because the enthusiasts are doing it for free that makes it viable. When a corporation manages Linux software, even if the software is freely available, they're paying for support time -- and if they're developing the software, as in this case, the development time.
exactly!
Another way to see it: engineering is the easy/cheap part. Testing, supporting, maintaining and marketing are way more expensive, and those are long-term expenses. The enthusiast usually thinks about the engineering bits, and when he's done with it he's done with it. Enterprise software is not like that - or shouldn't be :)