Multiple openvpn clients on one openvpn server

Solution 1:

Yes, you can. By default, OpenVPN server doesn't allow multiple clients to connect with the same pair of cert/key; each client must have its own cert/key with an unique common name. However, multiple clients are allowed to connect to the OpenVPN server using the same pair of cert/key if duplicate-cn (allowing duplicate common name) is present in OpenVPN server's configuration file.

Solution 2:

Yes you can use openvpn for multiple clients, but you'll have to setup a CA Authority and issue a unique key/cert to each client. Or setup password-based authentication and use the --duplicate-cn option.

Solution 3:

I believe it's fine if every client uses their own certificate, meaning that you need to issue a certificate based on the same common private-key to each client.

It's the certificate that is the actual authorization, since there are no login-credentials with OpenVPN.