Yes, the setup.py file lists dateutil 2.0.0 as a dependency, whereas calibre is currently packaged with 1.5 - but from a quick look at the code it seems to be compatible even though the dependency says otherwise.
As for simplejson, I have just pushed out 0.8.2 which uses the bundled json module rather than simplejson - it seems to do the job fine, so no need to bundle simplejson in the plugin
