AMD made an open source driver for HDMI 2.1 but HDMI forum won’t approve. They locked down the specification for 2.1 and say the driver would reveal it.
https://www.howtogeek.com/hdmi-forum-open-source-drivers-hdmi-2-1/
I don’t know if an earlier version can do 8k@60HD.
As long as you follow the GPL license you can redistribute it, for free or at cost. Linux is mostly free as in freedom and usually free as in free beer.
Wikipedia says ElementaryOS has a pay what you want model. So if your image is from them then you don’t have to pay (a 3rd party is free to charge you for it - bandwidth ain’t free).