We are using Unity3D for our game development platform. Unity's support of Linux at this time is limited - per the official Unity website:
The Linux desktop publishing preview is a work-in-progress. The Linux OS runs on a variety of hardware and utilizes different software. It will take more testing and feedback before Unity ships a final version. Many games will run without Linux-specific problems on most modern Linux systems. While in preview mode, we will only be offering official support for Ubuntu 10.04 or later, with a graphics card that has vendor-made drivers installed.
At Joe Got Game we don't want to promise you something we can't reliably deliver. When Linux support for Unity3D solidifies we will certainly explore publishing to Linux.