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As far as I know, yes. Check out their FAQ for how to go about. It's still important to source and reference the artists properly. https://ncs.io/usage-policy

So, NCS is only allowed in YouTube, twitch and Instagram. It's not allowed in 3speak, even if we give credit, right

I would guess it's ok to use on any platform where you monetize content as long as you put down the sources. But I don't know. You could try contacting them and asking. :)