Toradex provides Linux support for all other than the PXA module family in house.
You can find the latest binary releases here: http://files.toradex.com/Colibri/Linux/Images/
For Colibri PXA modules Android/Linux BSPs are provided as-is. Support is currently limited and Toradex is not actively developing or maintaining them at present. http://files.toradex.com/Colibri/Linux/Images/PXA-as-is/
For information about building U-Boot and Linux kernel from source code have a look here.
Check the Colibri Recovery Mode to learn how to program Linux on to a Colibri T20.
Furthermore there are open source projects from 3rd parties which provide support for the Colibri modules.
There is also some community activity about Linux support for the Colibri module:
Please let us know if your Linux community site is missing in this list.
At the moment this is only supported by the Colibri PXAxxx
You must convert the UBoot rom file as follows:
CreateTBin uboot.rom -a 0x0 -j