Chargebee - Chargebee lets you manage subscriptions and payments at scale, handle custom recurring billing scenarios, reduce subscription churn and simplify accounting.

Codezero - Collaborative Local Microservices Development

Recurly - Subscription billing and recurring billing management. Recurly offers enterprise-class subscription billing for thousands of companies worldwide.

LeadMD - LeadMD is the revenue performance consultancy that cuts through the BS by making your vision actionable and your outcomes measureable

Zuora - Zuora creates cloud-based software on a subscription basis that enables any company in any industry to successfully launch, manage, and transform into a subscription business.

Sirius - An open-source clone of Siri from UMICH