Bo and Ulf Andersson have a notice on their front page of their website. The  thank you is a final note of sorts, thanking publishers, developers, and others within the gaming developing industry that they have worked with

The reason for the closure was "too many publishers have been delaying their payments, causing an unbearable cashflow situation." Within the post they refered several times about integrity and honesty. Even directly thanking the crew at Capcom US "Thanks for being honest, a rare gift."

GRIN also revealed that they were working on a unannounced game, mentioning that they "weren’t allowed to finish."  I’m sure we can speculate all day. What game it is, and was this title pulled from GRIN and finished by another developer or will it just lay around.

With a decent library of games over the last 12 years: 
Ballistics (2001 - PC)
Ballistics Arcade (2002 - Arcade)
Bandits: Phoenix Rising (2003 - PC)
Tom Clancy’s Ghost Recon Advanced Warfighter (2006 - PC)
Tom Clancy’s Ghost Recon Advanced Warfighter 2 (2007 - PC)
Bionic Commando Rearmed (2008 - PC, Xbox Live Arcade, PlayStation Network)
Wanted: Weapons of Fate (2009 - PC, Xbox 360, PlayStation 3)
Bionic Commando (2009 - PC, Xbox 360, PlayStation 3)
Terminator Salvation (2009 - PlayStation 3, Xbox 360, Microsoft Windows)

GRIN can be proud of what they accomplished. As they mentioned on their site. "It has been a great adventure and the GRIN family has experienced what few have."

GRIN, you will be missed.