English compound nouns can be open, hyphenated or closed. What is acceptable usage changes over time. Some say that compound nouns "harden", e.g "file name" became "file-name" became "filename", and they all mean the same thing, but currently "filename" is the most common spelling. "Foot ball" was acceptable in the 1800s but only "football" is acceptable now.

Your example, "copyright", has only existed in this closed form. "copy-right" and "copy right" are not recognised.

On the other hand, "demo scene" is a recognised variant of "demoscene". It may look as wrong to you as "color" looks to me, but it's recognised.

Want a citation or two?

The Death of Kefrens (1991):

https://ftp.scene.org/mirrors/amigascne/Scrollers/K-Groupste...

    ORION, CODER:                           
    -------------                           
    LEFT THE DEMO SCENE FOR ABOUT A WEEK AS 
    HE STARTED CODING A GAME.               
    AFTER A WHILE HE CHANGED HIS MIND, DID A
    DENTRO, AND RETURNED TO THE DEMO SCENE. 
    NOW A MEMBER OF FLASH PRODUCTION.

How about "Break's Amiga Demo Scene Collection"? http://arabuusimiehet.com/break/amiga/

Or this 2007 interview of Fiver2? https://www.hugi.scene.org/online/hugise03/hugi%2033%20-%20d... "How do you think Debris will influence the demo scene?"