More or less what they use. I think some of the additional modules are probably not though (ie. animals and ADF modules).
Due to the US Military's reluctance to deal with international companies they deal with the homegrown company Coalescent Techologies. The actual company developing it is based in Australia.
I have VBS and several modules but on examination if you do not own OFP, including resistance, then purchase that and the high quality user made addons first to see if that would satisfy your taste as this requires the user to develop their own scenarios to get the full use out of it.
It comes with sample missions but they probably don't do its capabilities justice.
The main forum where you can see some people's reviews and comments is at http://forums.ogn.com.au