I think there is a flaw in your assumption in comparing an embedded application (MySQL) with a web based system. SugarCRM learned this the hard way, when their product was forked and released as vTiger, causing them to modify their license. This fork was not due to a community feud, but solely for economic gain.

Dual licensing works extremely well, as you know with the SpikeSource model, where anybody wanting to prevent the GPL viral effect, have to pay for a commercial license.