Wit.ai is a natural-language platform from Meta for building apps and devices that people can talk or type to. Developers send text or audio to the Wit.ai HTTP API with an access token and receive structured information extracted from it. Official libraries exist for Node.js, Python, Ruby, Go, Unity and Unreal, among others; the Unity library is a core component of Meta's Voice SDK. Wit.ai is delivered as a hosted API, not as software you host yourself.
Wit.ai belongs to Meta, a US company; the Wit.ai GitHub organisation lists Palo Alto, California, as its location. With a hosted service run by a US parent company, US law such as the CLOUD Act can apply to the text and speech sent to it. The service itself is not open source; only the client libraries are published on GitHub. The sources consulted give no hosting location for the service. A European organisation that processes speech or customer messages should weigh this and can ask Meta where the data is processed.