I think the difference is that PyPy exists, so people who just want "a faster Python" tend to go there, whereas in ruby-land JRuby gets the people who just want "a faster Ruby" as well as those who want Ruby on the JVM.

Honestly I wouldn't recommend trying to use Django on Jython (I'd be amazed if it all works), or really doing anything on either Jython or JRuby unless you're already familiar with all of the pieces. To understand and debug Jython properly you need a good understanding of both Python and Java. For a first JVM project, find something good and idiomatic in Java (I hear good things about Dropwizard) and use that.