Funny enough I was just playing with that trial for Laser Etch 15 mins ago, it looks very promising and for $30 not too bad of price, if it works. Of course I don't even have my laser yet to even try it LOL.
The only other (free) option, which is actully the tutotial you listed Inkscape addon, by the same company. http://jtechphotonics.com/?page_id=2012. Which I only got to show up by throwing the files directly in my Inkscape extensions folder (and had to copy something over or another LOL).
As for the Slic3R parameters for cutting, I have been lost there... I can't find any setting that the L-Cheapo people listed as "scale the Z axis; just set it to -1". I have been discussing this with them, so if I get an answer, I will report back. I think this must be critical to making it adjust after each layer in Slic3R to cut as opposed to just engrave.
Tammy
Solidoodle 2
E3Dv6 Hotend, MK5 v6 version, Glass Bed, Anti Z backlash slop nut, SureStepr SD8825 1/32 Extruder Driver, makeshift breakaway plexiglass case; . L-Cheapo 3.8 Watt Laser Attachment w/Custom built enclosure
From Buffalo, NY, USA