For 3) they are "Amen source", meaning that I pray a lot when I write those script, and for some reason they finally work.
They are fully readable, and I mostly write them for the fun of writing them: proper implementation would require some high level language knowledge I haven't, so feel free to take inspiration from them, although I am sure anyone would come with a better solution for most of the tasks they perform.
For your question, Icaros is part open source, part not. AROS IS NOT LINUX, there's less politic involved in code development here: this community appreciates open source but can also live with closed applications without getting mad.