As directed in MDL-16646 by Michael, I'm opening a new issue (and proposing a patch for it). Quoting from MDL-16646:

There are several mis-spellings, grammatical errors, and confusing language on the CAS configuration page.

1. Version - this currently says "Version of CAS". This is very confusing because what it is really asking for is the protocol version of CAS not the server version. This should say something like "CAS protocol version" The field label should be changed as well to reflect what is really being asked for.

2.Proxy mode - Currently says "Turn this to 'yes'' if you use CASin proxy-mode" should be something like "Select "Yes" if you use CAS in proxy mode."

3. Logout CAS - Currently says "Turn this to 'yes'' if tou want to logout from CAS when you deconnect from Moodle" should say something like "Select "Yes" if you want to logout of CAS when you disconnect from Moodle" The field label should be changed to "CAS Logout Option"

4. Multi-Authentication - Currently says "Turn this to 'yes'' if you want to have multi-authentication (CAS + other authentication)" should say something like "Select "Yes" if you use multiple authentication plug-ins (CAS + other authentication)"