They have foregone Red Hat Enterprise Linux because of maintenance costs
The justice system in India has been directed by the Supreme Court of India to switch from Red Hat Enterprise Linux to Ubuntu 10.04 LTS.The most probable reason for this decision is the fact that Red Hat Enterprise Linux actually costs money to support and Ubuntu 10.04 LTS from Canonical doesn't.
Sure enough, they will need a lot of people trained in the art of Linux, but Ubuntu has become increasingly easy to use in the last couple of years.
They chose Ubuntu 10.04 because is the latest LTS (Long Term Support) release developed by Canonical.
With the Long Term Support (LTS) version users get 3 years support on Ubuntu Desktop, and 5 years on Ubuntu Server, and all the updates are free of charge.
The next Ubuntu LTS version will be 12.04 (Precise Pangolin) and it will be launched next April, on the 26th.