It's been so long that I can't even find the agreement that I signed with Springer back then. But I would assume that there was something in there that allows them to do what they did. And since it's more than fine by me that the book is now available for free, I don't care. But if you're concerned about the issue, then, in my opinion, there is only one course of action: have your agreement with the publisher reviewed by a lawyer before you sign it.