If you hava an android vpn app which make a HTTPproxy or SockProxy, it will not be able to acces to the same Local area network. This app simply open another port which can be accessible to the local area network... Data comming to this port will be redirected to the port which is open by the vpn... by doing this the vpn service can be access to other device in the lan without installing the vpn service...
apk:-> https://github.com/ProjectUNBI/PortOpener/blob/master/generatedAPK/tablet_app-debug.apk