Answer
Two options are available: a commercial option which is provided as linkable object files, and an open source option. Both options are free when used with microprocessors connected to a Cypress Wi-Fi chip. The commercial option, ThreadX/NetXDuo from Express Logic, provides full IPv4 and IPv6 networking functionality. The open source option, FreeRTOS/LwiP only provides IPv4 networking functionality. https://community.cypress.com/docs/DOC-1168