This is Editor from OffiX --- part with desktop package with 
DND Drag & Drop protocol support.

Editor is an Athena based text editor. It's a patched version of the xed
editor. Like xed, you can perform common actions via user-friendly menus.
You can also drop a file on the "filename" area and the editor will load
this file. If the file is saved, you can also drag from this area to
somewhere else (e.g. to the "printer" program).

Check the OffiX main page below:

WWW: http://leb.net/OffiX/