The software and its documentation (Software) is shared thanks to the Vanilla Tweaks' Terms and Conditions.
You are allowed to use, modify and share the Software under the same conditions as listed below:

Also avaliable at: https://vanillatweaks.net/terms/

Vanilla Tweaks ─ Terms and Usage

It is perfectly fine for anyone to use, modify and share our packs within their projects for the betterment of the community.
However, you may only do so if it does not infringe on the following terms and conditions:

Section 1 - Terms
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1.1. You cannot redistribute our tweaks as they are, without proper modification and/or additions.

1.2. You cannot restrict access or sell any pack that includes our tweaks through donations and/or a paywall.

1.3. You cannot distribute our tweaks without appropriate credit (refer to Section 2).

1.4 You can distribute your pack with our tweaks, as long as your pack includes proper modification and/or additions.

1.5. You can distribute your pack with our tweaks, as long as you have appropriately credited Vanilla Tweaks (refer to Section 2).

1.6. You can distribute your pack with our tweaks, as long as it is free to use for the community.

Section 2 - Credits
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2.1. You must include the below text on all main publishing platforms that you may use. (Minecraft Forum, Planet Minecraft, Minecraft Maps, Curseforge, etc.).

2.2. You must create a credits.txt within your project that includes the below text.

Credits:
Vanilla Tweaks: https://vanillatweaks.net/