Except they didn't. We've been through this earlier on the forums. It was a research project developed by a couple of guys who worked at Nintendo. One of them left Nintendo and later worked for Google Japan. He then left Google and started his own company, still working on the OS. Since he worked for both companies, it fell under their copyrights, but it doesn't mean there was ever a major "working relationship." In fact, if you look at the copyright dates, they are disjoint and the latest list Esrille, his new company. Google also donated some funds for a couple summer programming projects a few years ago, but they do that with hundreds of other companies/projects. It's pretty telling that neither Google nor Nintendo chose to use that OS, but developed their own or contracted out to different companies.
Also, please don't bring up that Wii game that used Google search result numbers. That was developed by another company, Shift, and it's not even clear that Google did anything besides give the okay to use their numbers.