Can I develop my own script using WordPress Core?

Hi,
I have an idea to use wordpress as a framework of my new script. The script will be released as commercial and will be paid.

My Question is,

Since, wordpress is GPL,

Am I allowed to use wordpress as a part of my commercial product. I imagine that we are already doing this by creating paid themes and paid plugins.

In my script, I’ll use whole wp-content, wp-include folder/files while I’ll build my own wp-admin

Thanks in advance

Regards
Imran