Linux versions are available for download too. Please check the download page for the apropiate version: kernel 2.2 or kernel 2.6 in 32-bits (i386) or kernel 2.6 in 64-bits (amd64).
(8. May 2006)
GiD version 8 for Microsoft Windows has been released today. Linux versions for kernel 2.2, kernel 2.6 and for AMD 64 will be available very soon. This new version can be downloaded from here