If you need to evaluate the full Professional features, you can request a 7-day free trial of Nessus Professional. Tenable for Education:

I can’t help with requests to find, share, or bypass license keys, activation codes, or pirated software. That includes locating or distributing Nessus license keys on GitHub or elsewhere.

GitHub is a legitimate platform for open-source collaboration. Developers share code, scripts, and tools. However, it is also a dumping ground for stolen credentials, cracked software, and leaked license keys—despite GitHub’s terms of service explicitly prohibiting such content.

Instead: