Kojo-Web runs online based on Java Webstart Technology. You need to have Java 6 or later (Java 7 is preferred) installed on your machine to run Kojo via Webstart.
The first time you run Kojo-Web, all of Kojo is automatically downloaded to your computer (this might take a few minutes). From then on, it runs right away without any further downloading.
When an upgraded version of Kojo is released, (only) the changes made to Kojo are downloaded to your computer. So Kojo-Web always remains upto date.
Running Kojo-Web from outside a web-browser
If you have trouble running Kojo-Web from your browser, you can easily run it from a terminal/command-prompt by using the following command:
Java Security configuration for running Kojo-Web
With Oracle's increased focus on security, Kojo-Web (which uses a self-signed certificate) can only run with some Java security tweaks:
Java version 1.7.0_51 or later
Put http://www.kogics.net on the Exception Site List - by running jcontrol from the JRE/bin directory, clicking on the Security tab, and clicking on the Edit Site List button.
Java version 1.7.0_45 or earlier
Lower your Java security setting to High - by running jcontrol from the JRE/bin directory, clicking on the Security tab, and moving the Security Level slider to High. The High setting is pretty secure - you can run self-signed apps only with the latest version of Java, and you still have to click on a security prompt before an app can run.
Security Prompt before running Kojo-Web
Kojo-Web is cryptographically signed and published based on a self-signed Certificate generated by Lalit Pant, the creator of Kojo. Normally, Certificates signed by a well known Certificate Authority (instead of self-signed ones) are used for signed applications. As this is not the case here, Java Web Start will show you a big warning sign before running Kojo, and will ask you to trust the Publisher of the software. You will need to do so in order to run Kojo.
In case you have any concerns about this, you should be aware that Kojo is open source software, licensed under the GPL (v3). All of its source code is available for inspection.