I feel similarly to IgorBeg. Without going into too much detail about
Open licensing, so as not to drive Phyllis crazy making she to pursue
rare data lost in the menadirs of time, I would just leave a general
Authors window for all the code, without having to put them in every
file header.

thing is, file WITHOUT such header probably can cause misunderstanding (at best) down the line .... (not to mention distant possibility of court action by some wanna-be Microsoft/Apple)

so I think best course of action still fix most glaring omissions when possible, and then add details as we found them.

It is really good to get various opinions and is most helpful.

I will make an effort to gradually add headers where missing based on what information Andrew/I can find.

How about AUTHORS in the manual and then link to look there (so easy to do with HTML reference? Then we can say "mea culpa" for missing people, incorrect information like email addresses, and include credit for Testers, Manual Writing, YouTube videos contributions, and so on -- this could be more thorough, and hopefully would not make anyone feel bad.