Also, ed wasn't open source. Vi still used ed, so even of vi itself was open source, it wasn't completely functional. It was only around 2001 / 2003 when Calde

Also, ed wasn't open source. Vi still used ed, so even of vi itself was open source, it wasn't completely functional. It was only around 2001 / 2003 when Caldera open sourced some UNIX utilities under an open source license as part of the Heirloom project. Parts of that were ed and mailx.