Go to the Source
If you follow the Legal link at the bottom of the page and read the terms of service, among other things, it says (my emphasis):
1. Access to the Services
Subject to the terms and conditions of this Agreement, Stack Exchange may offer to provide the Services, as described more fully on the Network, and which are selected by Subscriber, solely for Subscriber’s own use, and not for the use or benefit of any third party. ...
Subscriber certifies to Stack Exchange that Subscriber is an individual (i.e., not a corporate entity) at least 13 years of age. ...
2. Network Content
... The Network is protected by copyright as a collective work and/or compilation, pursuant to U.S. copyright laws, international conventions, and other copyright laws. Other than as expressly set forth in this Agreement, Subscriber may not copy, modify, publish, transmit, upload, participate in the transfer or sale of, reproduce (except as provided in this Section), create derivative works based on, distribute, perform, display, or in any way exploit, any of the Content, software, materials, or Services in whole or in part.
Subscriber may download or copy the Content, and other items displayed on the Network for download, for personal use, provided that Subscriber maintains all copyright and other notices contained in such Content.
From time to time, Stack Exchange may make available compilations of all the Subscriber Content on the Network (the “Creative Commons Data Dump”). The Creative Commons Data Dump is licensed under the Creative Commons Attribution Share Alike license. By downloading The Creative Commons Data Dump, You agree to be bound by the terms of that license.
Any other downloading, copying, or storing any Content for other than personal, noncommercial use is expressly prohibited without prior written permission from Stack Exchange, or from the copyright holder identified in such Content's copyright notice. In the event You download software from the Network, the software, including any files, images incorporated in or generated by the software, and the data accompanying the software (collectively, the “Software”) is licensed to You by Stack Exchange or third party licensors for Your personal, noncommercial use, and no title to the Software shall be transferred to You. Stack Exchange or third party licensors retain full and complete title to the Software and all intellectual property rights therein.
3. Subscriber Content
You agree that all Subscriber Content that You contribute to the Network is perpetually and irrevocably licensed to Stack Exchange under the Creative Commons Attribution Share Alike license. You grant Stack Exchange the perpetual and irrevocable right and license to use, copy, cache, publish, display, distribute, modify, create derivative works and store such Subscriber Content and to allow others to do so in any medium now known or hereinafter developed (“Content License”) in order to provide the Services, even if such Subscriber Content has been contributed and subsequently removed by You. ...
Under Clause 2, everything on Stack Exchange is copyright and some things are trade marked as well. The copyright for posts vests in the Subscriber and is licenced to SE (CC BY-SA 3.0) or vests in SE directly as the creator.
Clause 8.1a. of CC BY-SA 3.0 requires SE to grant a licence to any recipient of a distribution (e.g. on a web site) on the same terms. For this reason the limitations on the copyright in Clause 2 can only apply to those items where copyright vests in SE directly; not to the content of the Subscriber posts.
Assuming that it is only Subscriber posts that they are reproducing then they either need to:
- Comply with CC BY-SA 3.0 and attribute the work as required by that licence; what they have put up does not on the face of it do that because:
- They are referring to an earlier version of the licence
- Attribution under 3.0 is detailed in Clause 4.c. and this doesn't meet the criteria.
- Have been licenced by the original copyright holder; which seems unlikely.
- Meet the fair use criteria; attribution would not be required but would certainly be polite. Fair use turns on the specific facts of the case - on the face of it they could put forward a credible argument that their use is fair use.
Jurisdiction matters here; copyright laws are not uniform across the world. For example, Australian copyright has a much more limited "fair use" concept than the US and also creates a "moral copyright" of the author that exists independently of the copyright of the owner.
For signatories to the Berne Convention; the country of origin for simultaneously published works (which online posting is) and therefore the law applying is the country that gives the shortest term of protection. The convention is annoyingly silent of what that means if there is more than one qualifying "Country of Origin"; this leaves scope for litigants to try to apply the most favourable domestic law that could be applicable and the case could be brought in any of several jurisdictions. This is the stuff that makes lawyers rich!