I reached out to the folks at Springer and asked them whether the availability of 57,000 titles for free download had been some kind of accident. Here's the response I got:

> Thank you for reaching out to us. From time to time our titles may become available to the public for legal download. There is no guarantee that titles available will remain available permanently. The only titles that will remain available are titles marked as Open Access.

Thus, it sounds like what happened was an accident or publicity stunt. I expect access to remain cut off.

Maybe if we wait another 10 years we'll get access to some more books. It's a shame that I didn't get a chance to download any of the books but then again I already have a backlog of other books to read so it's no great tragedy to me.

I don't understand this at all. Does their contract language with authors allows them to give books away at random times...?

I'd guess that they can do it under some sort of promotional clause in the contract, something stating that the publisher doesn't need to pay royalties for promotional copies of any book.

I am not an expert on copyright law -- do you (or anyone) know to what extent I am legally allowed to share the books I downloaded from Springer's website while I could?

In particular, I am teaching a course this spring based on two Springer books that I was able to download yesterday. If I e-mail PDFs to all of my students, am I legally in the clear?

I am not an expert either, but it is unlikely you ever had the right to share the files in any way, especially as it seems the error had still the standard license, but with cost of 0.00.

I am quite annoyed by this revert -- especially by the fact that big publishers can generate so much good will just by a simple error that gets shared on the Internet, while the correction will get minimal exposure.

Unfortunately, I do not think that you may legally share the works. Their terms of service currently say:

1.2 You may solely for private, educational, personal, scientific, or research purposes access, browse, view, display, search, download and print the Content.

1.3 You may not: [...] re-distribute, reproduce, or transmit the Content by any means including electronic (e. g., via e-mail) nor post it on their personal or public websites or on public networks...

So while you may have the copy of the book legally, it seems unlikely that you can give it to your students. There's always a chance that what they're saying isn't legally enforceable (see non compete agreements), but I don't think that's the case here. I'm not a lawyer, so I can't say for sure.

Depends on what license was communicated with the books when you downloaded them (or that is in the books themselves).

If there's no license specified, default is "all rights reserved" and you cannot distribute the books to your students free of liability.

This might depend on the country you're in. E.g. Polish law allows sharing of copies of works such as books between people who know each other (the exact condition is more involved, but boils down to essentially this).

Many books are indeed available for free download (including non-CS books), but most of the ones linked in this thread aren't.

Examples of working links: http://link.springer.com/book/10.1007/978-1-4302-5927-5 http://link.springer.com/book/10.1007/978-1-4302-6131-5 http://link.springer.com/book/10.1007/978-1-4842-0100-8

Those links are to "Open Access" books and have always, I believe, been free (as in beer).

The content identified by the original post were not open access; they were paid access (typically quite expensive) and published in 2004 or before.

I hope the zero cost downloads was not a glitch but a policy, and that Springer will make those older texts freely available again.

I hope nobody gets fired for this. Probably a lots of these leaked books will be up on torrent sites.

* Probably a lots of these leaked books will be up on torrent sites.*

If I had to guess, I'd say a pretty good chunk of them already were on torrent sites or LibGen.

That makes me wonder if after hitting a certain threshold in popularity they convert it from free to paid content.

I have access to SpringerLink as an Edinburgh University alumnus, through their contract with the university library. This means I can download a large number of their titles (not just the OpenAccess ones) apart from some restricted content (referred to as Preview Only Content when searching.) This includes many recent books and journals, all downloadable as PDF or EPUB format. For example the 'Praxis' series on spaceflight is excellent, including a book on SpaceX [1] among many others. The other cool thing this offers me is the ability to buy a thing called a MyCopy Softcover Edition version of these books for only GBP/EUR/USD 24.99 rather than the usual GBP 100 price for the hardback, which is pretty awesome if you like having actual, physical books to read...

So, I suggest you have a look into this and see if you can also get access via the academic login page and Shibboleth or Athens. Or, if not available to you personally, you may be able to just go to your nearest university library and get access to the books that way, too...

[1] http://link.springer.com/book/10.1007/978-1-4614-5514-1

Through my university network the books are still available (and have been for years). Might also be an interesting option for anyone living near a university with an open library.

OP link lists 66,327 results (i.e. books) available free of cost.

It appears to be working well for me, so perhaps a temporary glitch.

EDIT: no, I was mistaken. I can "download PDF" but it looks like that's typically only introductory content and not the entire book.