Is there some sort of announcement from Springer about this? Specifically, one in which they state what the license is, e.g., CC-BY or CC-BY-SA or something like that? I'll bet they attached either the No-Derivs (ND) or Non-Commercial (NC) limitations, though -- would love to be wrong about that. In the PDFs I've looked at so far, they didn't bother to change the copyright statement at the front of the book, so they still all appear to be under traditional restrictive copyright, whatever new terms Springer intends notwithstanding.
-Karl