If nobody owns the copyright then it'd be public domain, which by definition is free software since you have the four freedoms with it.

The issue is that even that is legally dubious. Text generation programs have been shown to output chunks of copyrighted text verbatim, so it's possible someone actually does hold the copyright to parts of that code, you just don't know unless you do your due diligence on every bit of text that is output. Since neither the "author" nor the actual generator can "know" the provenance of the generated code it is very risky to assume it can be freely used.