Similar in style to Ecce, this editor is different most significantly in its internal data structures. Ecce used the "gap technique" (which was slightly modified later at some expense of complexity in order to give improved paging behaviour for cursor movements which did not change the file); whereas Edit uses a more complex linked-list data structure which was designed to be VM-friendly. I know the C version was written by Tony Gibbons; I'm fairly sure that the original Imp version was as well, although as with much of the code from the ERCC it is quite likely that it was worked on by many people.
Edit for EMAS/2900 (includes some 2900 embedded assembler)