I've checked th demo and it's awesome! However, the fonts look really bad, especially on 4k displays. I understend that sometimes fixing stuff like this might be a real pain in the ass, however, it will greatly improve the general look and feel of the tool, and will make it much easier to justify paying 10$ for this.
I can recommend checking out fonts like "Exo 2" (you can find it on fonts.google.com), but there are probably fonts that are better suited for this.