We haven't had any issues with the free notification service. They did release the code to host your own but I think you'd also have to rebuild and release thei

We haven't had any issues with the free notification service. They did release the code to host your own but I think you'd also have to rebuild and release their mobile app to use it, and that sounds like a massive hassle. I'm using it for a nonprofit, so $10/month per user is out of the question. Self-hosting and open source are critical to us also.