with strong copyleft licenses, businesses must give back, namely when expanding the program
A user is required to make the source open only if they create a derivative work of the copyleft licensed work, and only if said work was distributed to users. And if I remember correctly, it is only required to open the source to the users it was distributed to.
They do not have to do any profit sharing or donation. They are not even required to make the code open source if they merely use this program, or they interface with it. They are not required to do anything if they only use it internally.
What did the original kernel not support?