Resolution:
Properties in Batch commands are based on the Java Beans specification. In a Java class, you define methods which match a pattern to get and set property values.
For example, if you have a property called MyName, you can define two methods:
Public class MyCommand implements Command {
    public void setMyName(String value) {
        MyName = value;
    }
    public String getMyName()
    {
        Return MyName;
    }
    public int run()
    {
        ; //do stuff
        return Command.SUCCESS;
    }
}
On the Batch Registry page, adding this command to a Batch, you could then add a property with the name "MyName" and value "Bob" by entering these in the two text fields and clicking Add property.