When I want to install the tools with the Windows installer, I get security warnings: unknown publisher,etc. Why?
The Wisext project is developed by a single person through his free time and he cannot currently start the official procedures to erase these messages. If you are wary, what is normal, you can install the plugin via the official Sketchup Extension Warehouse.
The Wisext extension has got the Extension Digital Signature to be loaded at the highest security mode in SketchUp (see: Extensions Loading Policy).