I think they should charge for The Dude.
Why? At the moment, The Dude is a loss-leader for other MT products since it is so tightly integrated/bound. If you've got a The Dude installation, then surely you're more likely to buy MT products rather than a competitor's?
If there was a licence charge, we wouldn't be using it - we'd spend the money implementing a Nagios solution instead. This would give us more information and allow easy monitoring of devices The Dude doesn't cope well with (SIP, for example). I suspect that others would also move away to competing 'free' products. To be honest, a combination of Smokeping, Cacti and Nagios would provide most people with more information than they need.
That having been said, I would like MT to make an announcement regarding the future roadmap for The Dude. IPv6 support is missing for starters...