After digging some more and finding pretty much every possible interpretation on different media outlets, I just called Nick Riegger, the press spokesman of Fidor Bank AG.
According to my conversation with Nick Riegger:
Fidor Bank AG has already started implementing support for Ripple on their back end. They will first be on the lookout for business partners also using Ripple, in order improve channels for sending money abroad to other banks and business partners. Long-term they want to offer their customers access to any major payment protocol, including Ripple and Bitcoin. To that end they are closely watching the development of the Ripple network just as they are already doing with Bitcoin.
To me it sounded as if they will first use Ripple as a user, but are also considering to provide gateway services long-term.
At Bitcoin2014, I had the chance to talk to a Ripple Labs employee and fellow SE user, who outlined to me the immediate problem that Fidor Bank AG was hoping to solve: Previously, Fidor had been paying a third party to transfer funds between its own subsidiaries in different federal states of Germany. As the counterparty of such a transaction is still part of the own company, this was like "paying someone to transfer money bills from my left pocket to my right pocket", as he put it. Fidor is hoping that using Ripple for this purpose will substantially lower the cost for such in-company balancing at low risk, while Ripple Labs is hoping that the demonstration of such a use-case would find mimics, or perhaps will convince Fidor to use Ripple for a broader range of purposes, such as transfering money to business partners using Ripple, or even providing their customers access to Ripple by becoming a Gateway in the long run.