I believe that Mule Studio became Anypoint Studio. Is there a version of Anypoint Studio that is open source (free)? Specifically, I'm referring to the GUI workflow designer tool.
There is an answer to my question (thanks @Ryan), but it comes with a caveat. Yes, Anypoint Studio is open source but, by default, comes with the Enterprise runtime. One can download the Community Edition (CE) and use Anypoint Studio with that.
The caveat, however, is after taking time to configure a flow with the included DataMapper component, I received the following error when attempting to run my flow with the community edition. Basically, to execute a flow with DataMapper, you'll need the Enterprise version. DataMapper does not execute with the CE.