But what other options than going dual-license do you have if you want to do open-source in a sustainable way? MIT does offer nothing here, unfortunately.
There are many good business opportunities if your open source technology, without strings attached, gets popular. You could just sell professional support as part of subscriptions and verified builds. Later on, when you release a new version, you can still support the previous one or build migration tools that you include with subscriptions, etc.
And you know what? It was true. We changed the licensing to MIT for most of Opa (http://opalang.org), but maybe a bit too late.