Linux and Open Source software are very popular for low level embedded and control applications. Due to it's open nature the technology optimally fulfills the needs of users from the automation industry who build systems which have to be supported over a timespan of more than 15 years.
One of the "building blocks" of Open Source automation technology is the Human Machine Interface. JVisu was written with the needs of field control technicans in mind - you don't need programmer's skills to write your own machine visualisation frontend.
And, of course, JVisu is Open Source, meaning that there are no runtime licenses and the code is fully available in source code form.