Compatibility: 6.7.x and 6.8.x
You can define your own About dialog. To do so, you would use the SET ABOUT command. Once you have executed that command, selecting the About item will execute the method provided as a parameter. From this method, you can create your window and display your own About dialog. However, keep in mind that selecting the About menu item from the Design mode will always display 4D's default About dialog. This is not a real issue since your database will always run in the Custom menus environment.
You will notice that when displaying your dialog, 4D will add some information in the window such as the version of 4D or 4D Compiler that was used with your datbase. This cannot be changed. However, if you do not want to display this information, there is a workaround: in the method passed to the SET ABOUT command, create a new process to display your About dialog. Since it is in a separate process, 4D will not add this extra information in the About dialog.