Can I change all configuration to replace occurrences of "demo.eleckey.net" namespace with my own server?

The demo.eleckey.net namespace is the default value used in the shell protection wrapper and in the ElecKey Agent. It can't be changed, but it will not affect any operation of the web services. If you use the KeyCheck API instead of the wrapper, you will be able to create your own web service interface in your application and define your own namespace.