Their CEO is here in part because he's been with YC nearly since the beginning (he was the cofounder of Twitch and JustinTV). He's one of the first users of HN, and is definitely a long standing member of the community.
It's a marketing ploy only in the sense that they just launched public signups and wanted to let us know about it.
It's a marketing ploy only in the sense that they just launched public signups and wanted to let us know about it.