When you pay for private modules, you can:
  • Host as many private packages as you want
  • Give read access or read-write access for those packages to any other paid user
  • Install and use any packages that other paid users have given you read access to
  • Collaborate on any packages that other paid users have given you write access to
Publish unlimited private modules for just $7/month.

https://www.npmjs.com/private-modules