2019 update: After a few years working on several dozens of cloud-related projects, I can confirm “cloud computing” and “cloud” are the most common forms in French as well. “informatique en nuage” and “infonuage” do occasionally show up, but the original English is definitely more widespread and understood by French audiences.
With constant developments in the IT industry, new terms and concepts can be hard to translate. For a rather long time, there was no real, universally accepted way to translate “cloud computing”. There have been attempts to convert it in French, with contenders such as “informatique en nuage” or “infonuage”, but they never really manage to stick.
Currently, you will mostly find “cloud” left as it is in French, with or without “computing” depending on the source text (some will choose to omit it regardless). You will generally see it written with a lower case ‘c’, although I have seen some translators and translation guides recommending the use of an uppercase ‘C’ (update: from my experience, this spelling appears to be less frequent lately). Unless explicitly requested otherwise, you can use “cloud” in French safely.