Scientific Linux (SL) is an open source Linux release developed by Fermi National Accelerator Laboratory and the European Organization for Nuclear Research (CERN) and various scientists and universities.
The base SL distribution is Enterprise Linux, recompiled from source. Scientific Linux aims to prevent scientists at each of these different institutions from having to recreate a Linux distribution that meets their needs. Scientific Linux is similar to Red Hat Enterprise Linux, with a few slight modifications.
See “Linux Downloads: Top Linux Distributions” in Webopedia’s Did You Know section.