My primary motivation for asking this question is this uservoice suggestion. Jeff declined the ticket to make the SO software open source saying that it will take more time.
I’ve seen this before in various other pieces of software that have gone from proprietary to open source. So, my question is: why does it seem to take so long to make software open source? To me, it seems pretty simple: put your code on sourceforge and google code and be done with it. But there’s obviously something that I’m missing in the whole process.
(And before anyone gets the impression that I’m trying to be critical of Jeff or anyone else that delays open sourcing their software, I’m not. I just want to get an understanding of the process for open sourcing stuff and its costs.)
The main answer to your question has been given by others – getting the legal permission to do so (see the SO blog entry on Reverse Engineering the WMD Editor for an SO-related problem child) is often extremely difficult, even impossible.
What you describe – dumping the source – is not really Open Source. It is more akin to either AbandonWare or perhaps ‘Available Source’. An Open Source project needs to accept inputs from outside, and build a community. One of the criteria that the Apache Software Foundation uses for its incubator projects is "has it acquired a critical mass of contributors from outside the original authors?". This is a valid concern.
Note that neither AbandonWare nor ‘Available Source’ is necessarily bad; both make code available that would otherwise not be available (and provide some of the benefits of Open Source). But there is more to Open Source than that.
Also, there is management overhead in handling a truly Open Source project. That is not negligible.
And, finally, it is not unheard of for the code quality to be such that the authors would rather not make the source available for fear of ridicule. I doubt if that applies in this case, but it can in other areas of the software world.