There is no official word on when the game might be available for Linux
The last Humble Bundle that featured games was launched on September 18 and arrived with a lot of good titles, including one called Vessel. Unfortunately, it was unavailable at launch time for Linux and things haven’t changed.The Humble Bundle initiative always put multiplatform games on sale for the three major platforms, Linux, Windows, and Mac OS (with a few Android exceptions). When Vessel didn’t show up at launch, people weren’t too excited, but at least the developer left a small note.
“Unfortunately, due to some unforeseen issues concerning our Vessel ports for Mac and Linux, these versions aren't quite ready for prime time. We will be getting Vessel out to bundle buyers as soon as possible,” stated the announcement.
A month and a half later, there is no word on the availability of the game for the Linux platform and the developer has yet to issue any official statement.