This independently constructed answer library written in C# is made for .Net applications to interface with the DuckDuckGo Zero Search API. Though not officially supported by DuckDuckGo, the library is listed on the DuckDuckGo API documentation under supporting library integrations. DuckDuckGo is a search engine which distinguishes itself by not tracking its users or generating results based on its user's previous behavior. The DuckDuckGo Instant Answer API provides free programmatic access to many of the search engine's instant answers, pulled from over 100 independent sources.
With Twitter reducing its search history to four days, it is a challenge for applications that are dependent on search results, that went not days but even months back. Several applications have taken on the challenge to fill this void and are building search indexes on top of Twitter. Topsy is one of them and it's sharing its results as an API.