Sixteen Colors Draw is described as 'Open-source HTML5-based ANSI/ASCII editor'. There are more than 10 alternatives to Sixteen Colors Draw for Windows, Mac, Linux, Online / Web-based and Self-Hosted solutions. The best alternative is Ascii Generator 2, which is both free and Open Source. Other great apps like Sixteen Colors Draw are Playscii (Free, Open Source), asciiflow (Free), Charaster (Free, Open Source) and Monodraw (Paid).
Ascii Generator 2 (Ascgen2) is an application to convert images into high quality ASCII art - text that accurately represents the original image. The only program of its kind to support variable width fonts and real-time output adjustment and more.
Playscii is a powerful, open-source ASCII-based art, animation, and game creation tool. Advanced layer-based tools and import and export options are available through a familiar window system with the appeal of classic DOS development tools like QBasic.
Charaster is a browser-based editor for ASCII grahics and art. It provides a robust set of raster-style editing tools such as Line, Rectangle and free-hand drawing tool; all configurable by specifying the character, color and styling to use while drawing.
Monodraw allows you to easily create text-based art (like diagrams, layouts, flow charts) and visually represent algorithms, data structures, binary formats and more. Because it's all just text, it can be easily embedded almost anywhere.
JavE (Java Ascii Versatile Editor) is a free Ascii Editor. Rather than for editing texts, it is intended for drawing simple diagrams by using Ascii characters. It is like a graphics editor for editing texts instead of images.