Turns out, Valve has moved away from Piston before it was finished.
"Valve began some exploratory work with Xi3 last year, but currently has no involvement in any product of theirs," explained Valve's marketing head head Doug Lombardi.
Nonetheless, Piston remains powered by Steam on Linux and should be more or less equivalent to Valve's upcoming Steam Box, save for the trademarks and logos.
Jason A. Sullivan, founder, president and CEO of Xi3 Corporation confirmed that PISTON is not the official Steam Box, but asserted that Valve was involved in all its development stages until it was finalized and announced.
"The assumption of many in the media has been that Piston is the 'official' Steam Box. We've never said that and neither has Valve. That hasn't changed," he said. "But just because Valve may not 'currently' have any 'involvement with any product of (ours)' doesn't mean that such involvement won't exist in the future."