While I myself have only modified smaller codebases, modified forks of Firefox, Chromium, and GIMP (among many others) do in fact exist. Some of those forks ha

While I myself have only modified smaller codebases, modified forks of Firefox, Chromium, and GIMP (among many others) do in fact exist. Some of those forks have even gone on to become quite popular (although none yet as popular as their parent codebases).