There are no specific settings for this in the JobRoller admin dashboard, so it would require some customization of the default theme files in order to do what you describe. There is no encryption which would prevent you from doing so. Although you can add widgets to the sidebar, these are unfortunately not category specific.
In the case of your other question, again, whilst you can easily add widgets, they're still not going to relate only to specific posts/pages as it applies across the board. JobRoller itself does not have a related job category widget, but it does have popular jobs related widgets. This would be another feature that would require customization on your part.
Thanks for the feedback about the features section, we'll get this fixed up! ;)