The suit has its roots at the Computer Systems Research Group (CSRG) at the University of California, Berkeley, which had a license for the source code of UNIX from AT&T's Bell Labs. Students doing operating systems research at the CSRG modified and extended UNIX, and the CSRG made several releases of the modified operating system beginning in 1978, with AT&T's blessing. Because this Berkeley Software Distribution (BSD) contained copyrighted AT&T Unix source code, it was only available to organizations with a source code license for Unix from AT&T.