https://privato.pub lets you sell private Composer and npm packages. — Now all that’s needed are relevant package ideas.

PrivatoPrivato – Sell private Composer and npm packagesA private Composer and npm registry with license keys, Stripe payments and a customer portal. Sell PHP and JavaScript packages without the busywork.
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The main difference with private packagist is that clients contract and pay directly on your platform? You act as a marketplace for packages, that's it?