Online Operating System are usually Java based Operating System with GUI which can accessed through Browser and have basic functions of a real Operating System. Most of the Online Operating System are Open Source and usually a modification of desktop environment of reBOX application framework.
How these Online Operating Systems works
Online Operating System is a server side software tries to emulate the look and feel of usual desktop software and basic applications. Besides the base system there is also a set of special applications
Basically all of these Online Operating System runs in function comparable with any modern Content Management System like WordPress. Most Online Operating System requires Apache Server with Python modules installed. Installation of these Online Operating System are for this reason almost the same like WordPress, they requires a Database, usually relational Database like MySQL. Some practically uses PHP and Java to execute the commands.
Advantages and Disadvantages of Online Operating System