Looking for open source social network softwares to build a site like this one?

I am considering building a social network similar to this one and startups.com but for a different market. I am somewhat familiar with StackOverflow but looking for a platform that gives me more opportunities.
I want to be able to potentially add other features like a jobs section, more advertising space and offer "Fee-based PRO user" with extra features and so on to generate some revenue. Which other open source social network software do you recommend? Please keep in mind that I am not technical and initially I need to maintain the site myself and once it gains traction I can hire a web developer to help me. I also would like to have the software on my own server rather than hosted.

There was an open source project that cloned the StackOverflow engine using Django - you can find it here.

There are a lot of hidden leveling logic that's not viewable by default - so while it has the look and feel on the surface, there are plenty of optimization, spam blocking, community points, badges, et al - which are all developed without the original developer insight.

If you are experimenting with communities, the stackexchange has a 45 day free trial - which if you get traction enough to pay the subscription - may be cheaper than hiring developers to maintain the Django code. If your site becomes very successful - then of course you can either have the option of rolling out your own or having some serious conversations with Joel and Jeff.

just use Stack Exchange. It is built by the same people that built SO and it is in beta, so it is in free. Here is an example of one that our family built --> Homework Hub

It would be nice to know more about your feature list, as, a good part of the reason that people are willing to pay a monthly cost for the software is that it fills a need that other social networking sites are missing.

I am not certain, but you may be able to buy the software from Foggy Creek and then modify it, but, I am not certain what the rules are on modifying the source code.

I have been building a closed source version of a site inspired by this one for a different market (community based bug/feature tracker). http://community.mediabrowser.tv and http://meta.community-tracker.com I had a look at the open source options prior to getting started and decided that I am better off starting from scratch.

There is a massive amount of hidden work in SO like engines, sure, the UI looks really simple but it takes months of tweaking to get stuff to work the way you expect it. You need a really agile and tidy code base, to be able to quickly react to the changing needs.

The biggest hurdle is getting people involved so you can adjust parameters to meet your communities needs.

None of the open source options out there (to the best of my knowledge) have had enough traction sort the basic user experience, they are very new projects. The success of the stack exchange engine hinged on the fact that the code was well exercised.

If SE meets your needs and just needs a slightly different skin I would recommend discussing this with Joel.

Otherwise, I would say this is a really tricky problem that needs quite a lot of time to do right and requires a fair amount dedicated dev work.

Plone open source CMS, or Pinax?

You could try Elgg http://elgg.org/ - it might suit your purpose.