Keygen - A dead-simple software licensing API built for developers
@ctivate - Activation Solutions is a software license management system solution to protect your software product from illegal copying or distribution.
CodeMeter - License Management
Vector Vizor Software - Vizor Software manages the entire software estate, including on-premise PC software licenses, mobile app purchases and cloud service subscriptions.
Labs64 NetLicensing - Monetize your digital products and services
SoftwareKey Licensing System - SoftwareKey System is a set of software development tools that help programmers implement copy protection, license activation and management, metering, eCommerce, and business automation.