The Stack exchange terms of service have been recently changed since a sentence in them was perceived as too strict by many users.
The change was in this paragraph:
In the event that You post or otherwise use Subscriber Content outside of the Network or Services, with the exception of content entirely created by You, You agree that You will follow the attribution rules of the Creative Commons Attribution Share Alike license as follows:
a. You will ensure that any such use of Subscriber Content visually displays or otherwise indicates the source of the Subscriber Content as coming from the Stack Exchange Network. This requirement is satisfied with a discreet text blurb, or some other unobtrusive but clear visual indication.
b. You will ensure that any such Internet use of Subscriber Content includes a hyperlink directly to the original question on the source site on the Network (e.g., https://stackoverflow.com/questions/12345)
c. You will ensure that any such use of Subscriber Content visually display or otherwise clearly indicate the author names for every question and answer so used.
d. You will ensure that any such Internet use of Subscriber Content Hyperlink each author name directly back to his or her user profile page on the source site on the Network (e.g., https://stackoverflow.com/users/12345/username), directly to the Stack Exchange domain, in standard HTML (i.e. not through a Tinyurl or other such indirect hyperlink, form of obfuscation or redirection), without any “nofollow” command or any other such means of avoiding detection by search engines, and visible even with JavaScript disabled.
The part in bold (emphasis mine) is new. Before, we had the following situation:
- A writes an excellent answer on Mathoverflow, and wants to include the same words in his lecture notes or in a book.
- However, A is bound by the restrictions of the TOS. For instance, he cannot scan an annotated copy of his own lecture notes and put in on his professional web page: this would violate points b. and d. in the quoted text, as a scanned pdf does not contain hyperlinks.
- This seems overly restrictive: why can't A, the original author of the answer, do whatever he wants with it, for instance relicense it?
However, the following slightly more complicated situation could arise:
- A writes an excellent answer on Mathoverflow.
- B, who is a colleague of A and another Mathoverflow user, wants to include the same words in her lecture notes or in a book.
- B sends a message to A: "hey, your answer looks great, can I use it in my lecture notes? I'll cite you as the source of course!". A answers "sure!".
- Now B, as a MO user, is bound by the TOS. For instance, she cannot scan an annotated copy of her own lecture notes and publish it on her professional webpage, even if A agrees.
- This seems overly restrictive: why can't A, the original author of the answer, do whatever he wants with it, for instance relicense it and grant other people additional rights?
I am not a lawyer and I hope I am reading the TOS correctly this time. My proposed fix is changing the text to the following:
In the event that You post or otherwise use Subscriber Content outside of the Network or Services under the terms of the Creative Commons Attribution Share Alike license, You agree that You will abide by the following additional restrictions:
Note indeed that the four points listed there are not part of the CC-BY-SA license, but are additional restrictions imposed by Stackexchange. There's nothing about nofollow in the CC-BY-SA license, for instance, and links are required only "to the extent reasonably practicable" (in CC-BY-SA 4.0; the TOS do not specify a CC-BY-SA version, but link to the older 2.5 version, which does not mention hyperlinks at all instead).
(Incidentally, not specifying which version of the CC-BY-SA is to be followed looks like another weak point of the TOS).
