In the 01950s through the 01970s you almost couldn't use a computer at all without getting a custom keyboard for it, so that wasn't an extra obstacle for APL. (You couldn't connect your Smith-Corona or Selectric to a computer, and until 01963, teletypes spoke 5-level "Baudot" code.)
One of Stallman's first jobs was writing a text editor in APL in the 01960s.
One of Stallman's first jobs was writing a text editor in APL in the 01960s.