Yes, for all high availability scenarios you need more than one server. As for high availability in the web edition, all you get is log shipping, so you will need to manually fail over to another server if your primary dies.
The native client is a combined ODBC driver and OLE DB Provider for SQL server. It doesn't in itself provide high availability, but it can be used, for example if you were using database mirroring, to provide the name of the mirror server for automatic failover.