Well, like Apache for serving websites, BIND is the most popular DNS server on the Internet. If you look at a given DNS server, chances are it’s running BIND. And I’ve seen no reliability problems with it
So why does it run BIND locally?
Well, Virtualmin is trying to make your life easier… it’s assuming that if you add a give domain to your system, that it’s managing the DNS for it.
If that’s not the case, no problem, you can simply disable the “DNS” feature in System Settings -> Features and Plugins.
At that point, it’s also no problem to disable BIND and setup your server to use alternative DNS settings, such as the OpenDNS ones you mentioned.