It appears that - when you add a collaborator to a Descript project that Descript will automatically add your collaborator to their marketing email list.
This is a clear lack of 'informed consent' as required by the Data Protection Laws.
As such it's a breach of both GDPR and the UK DPA and could result in Descript getting huge fines. The UK ICO hands out multi million fines regularly for such antics.
If the emails were only about the collaboration then Descript would have a waiver under 'legitimate interest' but doing this to send marketing emails is a huge no no.
As I used to look after the data of 4 million customers I STRONGLY advise you to get a Data Protection expert in quick to review such practices as this before you get into very hot water with the authorities.
I joke not.
Oh and not assigning affiliate commission to the account owner if one of their collaborators sign up to Descript doesn't say much for your ethics either! Who brought the collaborators to Descript? The Affiliate!