The screenshot is of an open source command line editor for Dos, Windows and Linux called TDE which is short for Thomson Davis Editor.
As the website says “TDE is a simple, public domain, multi-file/multi-window binary and text file editor written for IBM PCs and close compatibles running DOS, Win32 (console) or Linux. TDE is suitable for editing batch files, binary files, text files, and various computer language source code files (with configurable syntax highlighting). The only limit on the number and size of files that TDE can handle is the amount of memory. Likewise, the only limit on the number of windows is the amount of memory. There is no preset maximum number of files or windows that may be open at any one time.”
What interested me with this was that the editor should work for Linux. It includes a viewer mode where files are loaded read-only, file search (text or regular), can load files as binary, run a file as a Macro and display several source files with formatting. It certainly sounds a loty better than nano which is a terminal editor.