I am sceptical.
First of all, ESA can already fly to the ISS with the Russians or whatever NASA choses as a commercial crew vehicle. That's part of the deal, right? So maybe ESA plans to contribute to ISS operations with Dreamchaser participation? (similar to the SM of Orion). I don't like the sound of that, at least not in the case of commercial crew.
In any case, its very unlikely that ESA would fund an american company to build a crew vehicle for them. I don't think that is how ESA works.
Regarding launch on the Ariane 5, that seems to be another ploy from the DLR to keep Ariane 6 from happening too soon.