Torque 3D is the game engine out of Garage Games as the successor to the original Torgue Game Engine Advanced (TGEA) but with modern functionality like deferred lighting, NVIDIA PhysX, and modern shaders. The original Torque Game Engine had been originally developed in 2001 for the Tribes 2 game but it's been developed much more extensively since its inception.
It was back in September that Garage Games decided to open-source the Torque 3D engine. The open-sourcing of the engine was done under the MIT License. Garage Games earns its revenue from licensing Torque 3D for commercial titles as well as custom engineering, training, and offering other resources to game developers. While the engine code has been open-sourced for months, there's yet to be any native Linux client.
With Steam on Linux, the success of the Humble Indie Bundles, and various Linux shops (e.g. the Ubuntu Store) coming about, Garage Games finally sees Linux as a potentially profitable opportunity and feel they can compete in the emerging Linux gaming space.
In order to finance the native Linux work, Garage Games has turned to starting an IndieGoGo campaign where they hope to raise about $30,000 USD in order to finance the port. Their planned Linux port would be their full tool-chain for offering native Linux game development. This Torque 3D plan would allow game developers to develop their software entirely on Linux rather than some game engines where there is Linux support but all of their content creation and game development utilities are bound to Windows / Mac OS X with only export capabilities to Linux.
Garage Games announced this Linux initiative via their blog. They also created a video (embedded below) about their Linux plans.
For those not familiar with the Torque 3D engine, embedded below is one of their demos to showcase the current 1.2 version of the game engine.