I can't answer for jdf, but, in my case, I've built a lot of applications using Django and Google App Engine on very frugal hardware, probably less than a more recent Chromebook. On both cases, the development environment is very light and defaults to store data in SQLite. Working with Python allows me to skip compiling stuff most of the time. Of course, a JVM is off the table, as is using Eclipse for your IDE. This machine is one of the reasons I went back to Emacs.