Matrox has posted drivers for XFree86 4.01 on its website.
The README says:
“This beta driver adds new features to the currently existing
XFree86 mga driver. It includes support for the Matrox G450, G400,
and G200 graphics adapters. Newly added features include DualHead,
digital flat panel, and TV out support for the G400, DualHead
support for the G450, and multiple display support for the G200
Multi-Monitor series. This driver is also programmed to set the
internal clock speeds to production levels, increasing 2D and 3D
performance under XFree86.”
“This driver can either be installed by adding the mga_drv.o
module to a working installation of XFree86 4.0.1, or by compiling
the module from source.”
“The driver is for x86 based architectures only. Support for
other architectures is planned for future release.”
“Please take note that this is a beta driver and is not
supported by Matrox.”