It is a free plugin, remember?
Also, providers are specified within the plugin description:
The buttons offer login and registration using a Twitter, Facebook, Google, Yahoo or WordPress.com account.
Yes is free and that is really nice. But it is still not useable for me or anyone needing to use another OpenID provider. It might not be the authors fault, but the plugin is listed when I search for a OpenID plugin so I installed it and was disappointed.
Why limit it to specific providers?
I don’t know why the plugin was listed when you searched for OpenID plugins. As Ciudy said, the plugin description clearly specify the list of supported providers.
I’m not the original author of this plugin so I don’t know why it was created supporting only Yahoo and Google instead of supporting any OpenID provider. Actually I have asked myself the same question when I started maintaining it.
It is on my list to change this and support any OpenID provider but I’m not sure when I will have time to implement it. If you are a developer and you would like to contribute, patches are welcome. See https://github.com/thenbrent/social-connect/issues/44
All right I may not have been fair with my low rating (not sure if I can revoke it tough). I really hope you find time to extend the plugin – unfortunately my php programming skills is limited so I cannot be of much help.
From the home page of the plugin you can change your rating by clicking in one of the stars under “My rating” section.
About OpenID plugins, have you checked WordPress OpenID (http://wordpress.org/plugins/openid/) ? I’ve used it before and it is a great plugin.
