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StackOverflow is a collaborative Question and Answer community for developers.

Part of what makes the site great [...] is going to be the listeners, the people using the system. So I want to do the right thing in terms of licensing their content, so we're not abusing the relationship. — Jeff Atwood, one of's founders


The Stack Overflow communal question and answer site aims to be a repository for solutions to unusual or difficult programming issues. It is the result of a joint venture between Jeff Atwood, a well-known developer using Microsoft technologies and Joel Spolsky, CEO of Fog Creek, a small project management software company "intentionally designed to be pleasant"<ref name="ref1">Spolsky, J. 16 April, 2008. [1] Accessed 14 March 2009.</ref>. They approached Stack Overflow from a similar point of view.

Rather than a central body or single expert setting the agenda, the site looks to pool the collective knowledge of individual developers. While this might "contribute to the increasing dumbenation of the world's developers"<ref name="ref2">Atwood, J. Stack Overflow: None of Us is as Dumb as All of Us. 16 September, 2008. [2] Accessed 14 March 2009.</ref> by propagating incorrect information, the belief is that the 'collective intelligence' of the group will be able to respond to individual issues much more effectively than a single entity<ref name="ref3">Havenstein , H. 'Revolutionary' collective intelligence of users touted at Web 2.0 Expo.28 April, 2008. [3] Accessed 22 March 2009.</ref>. In this way, the site is similar to the free and collaboratively edited online encyclopaedia The validity of the content may not be checked by an expert, but through the collaboration of the site's users, the best solution will become obvious<ref name="ref4">Kolbitsch, J & Maurer , H. The Transformation of the Web: How Emerging Communities Shape the Information we Consume. Journal of Universal Computer Science, vol. 12, no. 2 (2006), 187-213. p193. [4] Accessed 17 March 2009.</ref>.

There are a huge number of forums and other web sites dedicated to discussing the spectrum of programming questions. Stack Overflow is one of the few programming related sites that attaches Creative Commons licences to it's content. It also stands out by combining a range of features usually kept separate, such as voting and collaborative editing.

As the site is still young, the issue of 'critical mass' is a concern – the point at which enough users frequent the site to make it viable and self-sustaining. Spolsky's view is that it will happen if useful answers are given. "Assuming that the question is very specific and that the person got an answer to their question, and that Google indexes us […] and then points to us when somebody else asks that question […], then that's all that it really takes." A properly built and run site will flourish, according to Atwood. "I don't think there's any particular point at which it suddenly becomes viable. Or, that point is a lot smaller than you think."<ref name="ref5">Spolsky, J & Atwood, J. The StackOverflow Podcast: Transcript 004. 15 September 2008. [5] Accessed 17 March 2009.</ref>

Although the solution to most, if not all, programming problems probably exists somewhere on the Internet, they can be very difficult to discover. The site's design aims to gather useful information by using elements of<ref name="ref6"> About.</ref>:

  • collaboratively edited information – eg.
  • user content submission, voting and comments – eg. and
  • answers to specific questions submitted by users – eg. and forums

While the site is hosted in Oregon, USA, people from all over the world access and contribute to the site. There are some American-centric aspects of the site, including discussions of copyright and other legal issues. The site has a small team of geographically distributed but US-based<ref name="ref6" /> developers, who maintain and improve the site and also act as moderators – they have additional powers for enforcing site rules.

Stack Overflow's business model focuses on sponsorship via advertising and utilising the founders' reputations to help promote both the site and consulting opportunities. The site utilises other small start-ups such as<ref name="ref7"> Stack Overflow Feedback Forum. [6]</ref> and also promotes the platform that runs the site: Microsoft's ASP.Net MVC framework.

License Usage

There are two Creative Commons (CC) licences in use on the Stack Overflow site. As part of the site's blog, podcasts are released each week, which discuss the current state of the site, and answer programming-related questions submitted as audio files. The podcasts are licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License. User contributed content is licensed under a Creative Commons Attribution-Share Alike 2.5 Generic License, also known as "CC-Wiki". It is a popular choice for community editable content and allows attribution to the website or individual users<ref name="ref8">Lessig, L. Code v2.0 and the CC-Wiki license. 17 March 2005. [7] Accessed 11 March 2009.</ref>. The programming community is likely to become more aware of Creative Commons licences due to the use of a CC license on the Stack Overflow site.

To indicate the licences, there are Creative Commons icons in the footer of the blog and main site pages. The blog footer also includes text indicating that the license applies only to the podcasts. Some confusion has arisen over how the CC-Wiki license applies<ref name="ref9">Stack Overflow. Is the content of the protected?. [8] and Stackoverflow’s Creative Commons license. [9] </ref>. There is no indication of the license when posting questions or answers, and it is not stated (as at March 2009) specifically what content the license applies to. While it is not strictly necessary, it would be beneficial to have some indication of the license and what it means for the user when posting to the site.

The use of different licences stems from the intended purpose of the content: the podcasts are mainly informational and promotional, so allowing only non-commercial remixing makes sense, but the Questions and Answers are more likely to be put to use in commercial projects. The use of a generic license for user content, and a United States specific license for the podcasts may be due to the site content coming from anywhere in the world, but the podcasts being made in the US. This aids in being welcoming to contributions from users globally, as the site currently has an overwhelming majority of US-based users. Around a third of the site's traffic (as at January, 2009) comes from the US, with the next highest being the United Kingdom at around 8%<ref name="ref10">Atwood, J. Where In The World Do Stack Overflow Users Come From?. 13 January 2009. [10] Accessed 14 March 2009.</ref>. Due to the predominately American users of the site, there are some differences in site activity at various times<ref name="ref11">Atwood, J. The Best Time to Ask a Stack Overflow Question?. 5 January 2009. [11] Accessed 14 March 2009.</ref>.

"Creative Commons is neat in that [...] when you create something, it is copyrighted by default. So when you [...] use Creative Commons what you're saying is, I want to give up some of my inherent copyright, so that other people can remix, reuse, benefit from […] stuff that's meant to go out into the world and be shared and reused. [...] And you can control that, and put rules around it."<ref name="ref5" /> - Jeff Atwood

Jeff Atwood considered how a CC licence would reflect on the podcasts before applying it<ref name="ref12">Atwood, J. Now Licensed Under Creative Commons. 5 May 2008. [12] Accessed 20 March 2009.</ref>. The comments to his blog post showed there was some misunderstanding regarding how the licence applied, but the general response indicated that users appreciated the fact that thought had gone into licensing. The CC-Wiki licence applied to the site content drew a similar reaction, and according to Atwood one user "seemed very encouraged that we were thinking about it and doing something about it."<ref name="ref13">Spolsky, J & Atwood, J. The StackOverflow Podcast: Podcast 010. 9 November 2008. [13] Accessed 17 March 2009.</ref>


The site's two main founders have both had experience with licensing in past projects. Jeff Atwood, while not a fan of licenses or legal matters in general, does believe that licenses are "a necessary evil for any code you plan to release to the public". His position is that the license doesn't matter so much as the certainty that comes with it<ref name="ref14">Atwood, J. Pick a License, Any License. 3 April 2007. [14] Accessed 20 March 2009.</ref>. Utilising a Creative Commons license serves to explicitly declare the conditions, but enabling sharing of the information – which also increases Stack Overflow's popularity - is the most important benefit for Joel Spolsky.

It appears that the choice of license was driven in part by observing what other similar sites had done to enable easy access to user contributed information. Stack Overflow crosses into a number of usually separate user interaction domains, however the core of the site is user questions and answers. "Part of what makes the site great [...] is gonna be the listeners, the people using the system. So I wanna do the right thing in terms of licensing their content so we're not abusing the relationship."<ref name="ref5" /> It is also important in terms of allowing editing on the site. The Creative Commons licence makes sure edits and modifications are legal, as the default copyright does not allow changes without the original author's permission.

The community behind Creative Commons licenses was a factor in deciding to use the license. Combined with the ease of using the "pre-formulated wiki Creative Commons license"<ref name="ref5" /> (or CC Attribution-Share Alike<ref name="ref8" />), the founders immediately looked to using a Creative Commons license.


During construction of Stack Overflow, the site developers constantly consulted the programming community regarding what should the site should aim to become, and how it should be able to be used. The reputations of Atwood and Spolsky were a factor in the site being talked about and becoming popular even before it had launched. Jeff Atwood commented that "we wanna get feedback from the community on what it is we're supposed to be building as we build it."<ref name="ref13" /> They continue to welcome feedback through avenues such as