We include a [script for Yubicloud](https://github.com/GluuFederation/oxAuth/tree/master/Server/integrations/yubicloud), which I think verifies the OTP code.
Also, there are some open source yubikey validation servers:
* [yubico yuvikey-val](https://github.com/Yubico/yubikey-val)
There is also a [python](https://github.com/Kami/python-yubico-client) and [java](https://github.com/Yubico/yubico-j) validation library, either of which could be incorporated directly into an authentication script.
If you have some budget, we'd be happy to manage a bounty on this feature. One of our subcontrators would surely take it on.