Asset store assets are not allowed either, except for the ones that don't contribute to the game itself but make the workflow easier. You can use the tools that are in the Unity Package manager, except for the standard assets.
Yeah, I know. I read the rules. I guess the real question is: Is Fungus considered an asset that don't contribute to the game itself but make the workflow easier?
Depends on what this asset does. I don't know it myself, but by reading through it's description it sounds like the code is already pre-made. So no, Fungus is not allowed in this Game Jam.
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Everything has to be made during the jam. This means you can't reuse any code or assets you made before the jam or from other sources.
All assets that make the workflow easier have code already pre-made. Take, for example, cinemachine, or 2D Pixel Perfect Cam, from Unity Package Manager. And they are allowed.
IMPOV, if you are looking at it's no-programming nodes, then you're good to go, but anything else from it, i wouldn't use it. If you know PlayMaker, then use the free version of it. ;)