The DiSo Project (well, wp-openid specifically) is participating in the Open-Source Identity System Interop Testing happening now until the RSA Conference in April. WP-OpenID is an OpenID 1.1 and 2.0 consumer, and additionally uses the simple-registration extension. We do not yet support attribute exchange. Under the covers, we use the JanRain PHP Library… a version somewhere between the 2.0.1 release and the latest code in the darcs repository.
Testers should be able to leave an authenticated comment on this page using any OpenID 1.1 or 2.0 provider. We are aware of a bug that prevents interop with Vox OpenIDs in certain cases. Please do limit OSIS testing to this blog post. If you run into trouble, you can contact me directly, or the DiSo Project List. Happy testing! :)