nvi

nvi (new vi) is a re-implementation of the classic Berkeley text editor, ex/vi, traditionally distributed with BSD and, later, Unix systems. It was originally distributed as part of the Fourth Berkeley Software Distribution (4BSD).

Due to licensing disputes between AT&T and the Computer Systems Research Group (CSRG) at the University of California, Berkeley, the CSRG was required to replace all Unix-derived portions of BSD source with new and unencumbered code. nvi was one of many components rewritten, despite the fact that the original vi was from UC Berkeley. AT&T had a legal claim over the license.