It is truly amazing that a language Microsoft have largely ignored for 15+ years is still so popular.
VB6 programming will last forever.
One thing to watch out for is UAC (User Account Control). If this is switched on (you can switch it off, but it isn't really advisable) this would prevent you using your .mdb database if it is in the Program Files folder together with your VB6 app. This was always bad practice, and now UAC prevents it. So you would need, for example, to move it elsewhere and modify your VB6 program accordingly.
There is no reason Microsoft cannot open source VB6.
It is just that Microsoft choose not to do this.
Are they still scared because VB6 is more popular than .Net?
Or do they hold all developers in contempt?