Question

The only things that are good about chess.com are puzzle battle and bughouse, right? Well, this probably won’t work, but could someone please explain to me why lichess can’t just right-click, inspect, copy all the code, and put it into lichess with a few modifications? I know it’s copyrighted, but since lichess isn’t trying to make money with it, isn’t it allowed?

That's how you get your pieces stuck in mud.

1. Only the client-side code is available. You could make a client that connected to chess.com servers, and that's it
2. It's minified javascript, and a lot of it - not exactly fun to develop
3. No, "not trying to make money" is not a defense to copyright infringement. Chess.com's license probably doesn't allow redistribution of the code, and I seriously doubt it'd be compatible with the AGPL license used by Lichess (see also: Why couldn't chess.com just copy Lichess? Their making money isn't a problem, it's their unwillingness to open source their own code)

I've asked this question many times in academia. Why can't I copy an entire book and just cite the source? How can people use speech writers and not give proper credit?

A lot of sites have these features, and they all have their own code. It is difficult to understand another's code and then to adapt it to your own. It would be easier and faster to develop your own code.

Better to ask (Why there is no bughouse on lichess) instead of saying (right-click, inspect, copy all the code, and put it into lichess with a few modifications?), because what you will copy is the display only, not the DBs and sockets and many stuff. :D

#5 Indeed, be careful what you wish for!

Lol someone should ask chess.com to get hired for coding and then give all the code to lichess