Currently Being ModeratedDec 28, 2011 6:46 AM (in response to Yaann)
The G5 would need Leopard Server installed on it. The standard Leopard does not have a VPN Server on it, just the client. There may be other VPN's servers you could install on it. Another possible issue is how your G5 network is configured. Is there a firewall? Ports need to be opened pointing to the VPN server...
A better place for answers would be in one of the server communities.