The article mentions four patents:

9,168,698 / 10,556,381 - Force detection on the printhead, ie when your printer homes the z-axis by touching the nozzle against the build plate (would not include conductive or magnetic sensors)

9,421,713 - Using purge towers in prints with multiple filaments or extruders

7,555,357 - Not really sure exactly what this describes, so here is the patent's abstract:

A method of forming a three-dimensional object using an extrusion-based layered deposition system, the method comprising generating a build path for building a layer of the three-dimensional object, where the build path defines a void region. The method further comprising generating at least one intermediate path in the void region, and generating a remnant path based at least in part on the at least one intermediate path.

Seems to include slicing objects that are not completely solid on the surface (ie a cube with a hole through the center).

So, with this precedent, Stratasys can go after.. nearly every printer on the market. Cool