Majority of ShaderToy shader MilkDrop presets are licensed with CC-BY-NC-SA 3.0, confirmed from ShaderToy's Terms of Service and Privacy Policy: https://www.shadertoy.com/terms
You aren't allowed to use these ShaderToy converted presets for commercial purposes. Use them with care and you must credit shader authors of you have used them.
Learn more: https://creativecommons.org/licenses/by-nc-sa/3.0/deed.en