I think the statement after that just pertains to the art and visuals of the browser. As a musician who doesn’t have art/design skills, I can understand the pain of building something but not having the skills to make it look good visually (i.e. album cover art and promotional materials).

EDIT: Nevermind, I misread your comment. Yes, they could’ve just said “I code everything myself”.

EDIT 2: For those replying there’s still Mozilla code in there, yes I’m aware. I was implying the code specific to Waterfox.