OSPF: how to advertise the subnet of an OpenVPN server?

The first thought that comes to mind is that you need to redistribute the kernel routes in addition to the connected routes in Quagga/Zebra OSPF. Because OpenVPN adds the routes itself, Zebra will not redistribute them if you only have 'redistribute static' in your configuration.

I am using OpenVPN in OSPF environments too, and everything redistributes just fine.

Note: you may need to add some redistribution list filters to prevent redistribution of other kernel routes that shouldn't be advertisted.

Another option is to add a static route in Zebra for the 10.180.1.0/24 going to null or the loopback device.