Would it be legal to just “clone” Photoshop or Lightroom as a FOSS project? I mean create a nearly exact clone. Everything down to the layout, tools, menus, op

Would it be legal to just “clone” Photoshop or Lightroom as a FOSS project? I mean create a nearly exact clone. Everything down to the layout, tools, menus, options, etc. Who would Adobe sue? Could they make it illegal to distribute?