OpenAthens is a federation of specific institutional members, and we are a member service provider within it. The term "Athens" can also refer to various kinds of software that can be used by customers who are either members of the OpenAthens Federation or members of a different authentication federation, such as UKAMF.
We support OpenAthens Federation members through the Athens dropdown box on our institutional login page.
We support members of UK Access Management Federation who happen to use Athens software through the Shibboleth dropdown box on our institutional login page. (Confusing, we know, and we hope to be able to combine the two).
There are some features of Athens software in the area of WAYFless linking that do not work with SpringerLink because we are outside the Athens software "universe" (we don't use Eduserv's software). Full integration with all Athens software would require additional development from both SpringerLink and Eduserv.
See also: Where can I get more information on Athens and Shibboleth?