in5 is automatically installed in Demo mode within InDesign until you activate it with a license.
Here's how Demo (trial) mode output differs from Licensed output.
1) The Demo mode adds watermarks to most images.
2) Demo mode limits certain options to 4 pages (e.g., the Flipbook Page Peel format, live text rendering, Responsive Layouts).
3) Demo mode won't let you test certain Pro (Gold or Elite) features (like Image Optimization and Interactive Widgets), but demo mode should at least give you an idea of how a licensed plan might serve you.
4) You won't be able to remove the in5 link in the footer of the exported document. Once activated with a license, you'll be able to uncheck the Show in5 Link in Footer option to remove the in5 branding.
The demo version has no time limit, so you can use it for testing as long as you need to.