How would a commercial venture plan to recoup their investment cost when (if) they finally reach a viable reactor design?

If an American/European company came out with a working reactor, would India and China pay for the technology, or would they put hundreds of billions into developing their own? What about the opposite scenario? Even a tiny peek at the design would shave off a large portion of the cutting edge investment. On the other hand, fusion could completely alter the course of climate change, perhaps it's cheaper in the long run to just give out the technology.