OpenSearch has a long history at Amazon. The trademark for OpenSearch is held by Amazon.
At the 2005 O’Reilly Emerging Technology Conference, Jeff Bezos showed the world the OpenSearch syndication protocol. This protocol was born out of A9, the search arm of Amazon.com, and allowed for the syndication of search results across services. This protocol has lived on and is still valid today. You can find more details on Wikipedia. This specification is currently being maintained in GitHub by an ex-A9 employee, at github.com/dewitt/opensearch.