Antonym for "derived"/"derivative"

Solution 1:

Consider underlying

In copyright law, a derivative work is an expressive creation that includes major copyright-protected elements of an original, previously created first work (the underlying work). The derivative work becomes a second, separate work independent in form from the first.

source: https://en.wikipedia.org/wiki/Derivative_work

Solution 2:

I think the term you're looking for is original (not the adjective, but the noun):

“Original” quite simply means a unique one-off piece or small edition hand-pulled print from the artists own hand i.e an oil, acrylic, watercolor painting, etching or a drawing (i.e. not a machine driven process like a giclee).

Additional definition:

When an artist creates a unique artwork, that is an original. That original may be a painting of some kind, or a sculpture, or a performance work, or one of many other kinds of media.

Usage:

Is that an original Picasso? That must be worth millions.

Possible response to demonstrate the contrast between the two terms:

No, it's merely a derivative. You can tell by the careless brushstrokes here.

Note that the terms derived (or, alternatively, derivative) and original (work) are also used in the legal context of copyright:

Most countries' legal systems seek to protect both original and derivative works. They grant authors the right to impede or otherwise control their integrity and the author's commercial interests. Derivative works and their authors benefit in turn from the full protection of copyright without prejudicing the rights of the original work's author.