tax-exempt

I'm trying to find out information about a Serbian non-profit operating in the US and many other countries around the world. (Centre for Applied Nonviolent Action and Strategies (CANVAS). If they operate in the US are they required to file an IRS-990, or is that only if their headquarters are located in the country? And if I can't get their tax info, is there any other information that foreign non-profits are required to file with our government, or am I pretty much out of luck?

I'm working on an article about a company District Energy, which is a non-profit that also operates a for-profit energy company called Market Street Energy. How common is the practice of non-profits owning for-profit businesses? How is it done legally? Can the money generated go directly back into the non-profit? Do these for-profit companies operate under any of the restrictions that apply to nonprofits, or are they regulated the same as any other corporation? Any info would be much appreciated.