For these to work, you will have to open your "Java configuration panel" (Oracle Java 8 plugin control panel), go to the security tab, set the security level from "very high" to "high" and add "http://www.madkit.net/" to the exception list.
The bees simulation
A Market organization (using the contract net protocol)
Multi Pong demo
TurtleKit: An artificial life platform
The MaDKit desktop mode demo
Alternatively, all these demos are available in the demos folder of MaDKit-5 releases.