Engage is described as 'PowerPoint add-in that lets people of any skill level create and automate visually impressive presentations with infographics, pictograms and data maps' and is an app in the Office & Productivity category. There are seven alternatives to Engage for a variety of platforms, including Online / Web-based, Mac, Windows, Linux and PortableApps.com. The best alternative is Apache OpenOffice, which is both free and Open Source. Other great apps like Engage are LibreOffice - Impress (Free, Open Source), Prezi (Freemium), Keynote (Free) and Ludus (Freemium).
Prezi allows anyone who can sketch an idea on a napkin to create and perform stunning non-linear presentations with relations, zooming into details, and adjusting to the time left without the need to skip slides.
We are Ludus, making a slides builder for creatives. We are mixing pro features from Sketch, with the power of internet (Sketchfab, Framer, CodePen ... are some of our integrations). So slides can be truly creative and limitless.