Dosage is designed to keep a local copy of specific webcomics and other picture-based content such as Picture of the Day sites. With the dosage command line script you can get the latest strip of a webcomic, or catch-up to the last strip downloaded, or download a strip for a particular date/index (if the webcomic's site layout allows this).
Multiple webcomics can be downloaded in parallel, making the update of comic strips faster.
These details are provided for information only. No information here is legal advice and should not be used as such.