Also, there are examples of "knock-off" TFs in other Japanese media, like the NSFW "Panty and Stocking" episode, "
Trans Homers".
And don't forget the "totally not for profit, honest" copyright lawyer's dream/nightmare that was the animated intro to the "Daicon IV" convention.
Doujin and other fan-made anime/comics/etc are also a thing too.
As for YouTube, Japanese media have always been fairly trigger-happy about allowing their media to be online and/or shown outside their markets. Such companies have, like many other aspects of Japan, arguably slow to change or adapt. I think at one time, NHK itself wasn't able to show reruns of its own shows at its only streaming service/website. I'm not sure how much of this has changed now but that's how things are in Japan. Yes, the copyright can be infamous when it comes to online/foreign access (in order to control the market) but in terms of homages and suchlike, in not sure if it's so strict.