The best free alternative to Pubnub is Firebase. If that doesn't suit you, our users have ranked more than 50 alternatives to Pubnub and many of them is free so hopefully you can find a suitable replacement. Other interesting free alternatives to Pubnub are GUN (Free, Open Source), MongooseIM platform (Free, Open Source), OneSignal (Freemium) and deepstream.io (Free, Open Source).
Databoom is a backend service solution for your WEB and mobile apps. Includes the secure cloud database, OData based query language, file storage, and more. Focus on creating front-end and stop worrying about server and database infrastructure.
Light SDK for mobile push notifications. Drive user engagement and customer retention QUICK Implementation under ten minutes. spend more time in actual development of your app rather than worrying about push.