Closest deployable software to current stackexchange software?

Are there anyone using stackexchange like Q&A for their product? How great has it been in building a community of helpers and engaging the user in how to use your software? I plan on making a Q&A section with running something like stackexchange software.

If you are using something like stackexchange for Q&A, which one are you running? open source or paid?

I use and recommend OSQA, the developers behind it have a long history and I'd personally trust them not to simply drop it. If you do use OSQA, enable the memcache feature though, makes a hell of a speed difference.

Check the link below.

http://meta.stackoverflow.com/questions/2267/stack-overflow-clones You can choose one for your site.