The rules are on the same page I linked (https://www.indiegameawards.gg/faq), under the "Game Eligibility" tab. I gave them the benefit of doubt and assumed that they had defined the exact terms of what is and isn't allowed, but apparently I was wrong. Regarding AI, the document contains a grand total of one sentence:

Games developed using generative AI are strictly ineligible for nomination.

I'm assuming the definition of what that entails is "at their discretion", meaning whatever they feel like at the moment. I see that sentiment reflected in this thread too.

It's possible that potential nominees have to sign some kind of declaration that they've complied with the rules, and that might include a more detailed list of rules, but I have no evidence to support this.

Unfortunately the boundary between "AI" and "not AI" is the polar opposite of sharp and well-defined. I've used Allegorithmic Substance Designer a lot for CGI work (before Adobe ate the devs; fuck Adobe, all my homies hate Adobe), and it contains a lot of texture generator algorithms from simple noise to complex grunge textures. Things like Perlin noise and Voronoi diagrams are well-known algorithms and definitely not AI. Chatbot slop is right out, but in between those two, things get remarkably fuzzy and Heisenbergian. What about an algorithm that uses real-world samples, like an image? Or multiple images? Machine learning is not the same as AI, so is that allowed? Where's the line? I'm reasonably certain that everybody has a different answer for different situations based on different criteria.