body: Let's say I have propriety software which I recreate using solely my observations of its user interface, input and output.
  
  
  I recreate this software to near-perfection leaving out only trademark icons and symbols.
  
  
  Then, I publish the source code of my rewritten version of the software, under a different name to the original program, on GitHub (or something similar).
  
  
  Does the owner of the original software have grounds to sue me or make me take my code down from GitHub? Is this still considered reverse-engineering even though I haven't disassembled the original binary or accessed the original source code in any way?
  
  
  
title: Can software be legally rewritten if the original source code is not used?