The licensing requirements for code contributions are clearly defined as MPL-2.0 in https://github.com/mozilla/voice-web. https://voice.mozilla.org/ has “Creative Commons license” in the footer linked to https://www.mozilla.org/en-US/foundation/licensing/website-content/. That states “Unless otherwise indicated, the text of documents in this collection is available under the Creative Commons Attribution Share-Alike 3.0 Unported license, or any later version.”
I can’t find any contributor agreement or indication in the UI of how the recorded “donations” are licensed.