Instead, it has signed up more than a million developers who use its software to build voice, video or text messaging features into apps, including WhatsApp, Uber and Airbnb. It makes money when usage takes off, charging fractions of a cent per user. The cloud-based communications supplier aims to sustain its lead in a market it pioneered eight years ago, teaming up with hundreds of rival start-ups and independent software projects, as well as giants Cisco and Avaya Inc. Twilio said it has agreed to acquire a team of ten Madrid-based developers and proprietary technologies they built for large group communications via video conferencing, file transfer, chat or desktop sharing and which don't require users to first download plug-ins. "This will be the basis of all of our next-generation, cloud-based media services," said Jeff Lawson, Twilio's founder and chief executive, in a phone interview.