The webspeech api is web based, which I think goes to Google if you're using Chrome or Firefox. It also has a fairly long lag (well over a second?) and is mostly suited to text dictation.
In that case I think the headline “open source voice typing” is not a good description. I would expect it to work locally with a headline like that. Not to ship off all of my voice data to Google and have them run the speech to text stuff.
In chrome extension i'm using webSpeech api, which sends voice data to google server and get text back, but one doesnt have to login in any account to verify. SO in a way google gets your voice data but that data is sudo anonymous.