OpenSC is a open source smart card middleware package. It can be used to enable use of Smart Cards in PKCS11 enabled applications such as the Firefox Browser and Thunderbird Email client. OpenSC supports Windows, Mac and Linux.
PIVKey is compatible with the US Government PIV standard, and will work with OpenSC.
OpenSC supports PIVKey (and other PIV cards) in Read Only mode. That is you can't use OpenSC to write certificates to the card, only to read and use certificates.
OpenSC may not support the PIVKey X.509 Certificate for Card Authentication (9E Key). That is because with PIVKey this certificate is secured with the User PIN.
OpenSC PIVTool does NOT support PIVKey administration functions, like generating keys and loading certificates.
OpenSC can be found here:
Two examples of applications that use OpenSC middleware are: