Yeah, as @rpegg notes: this tool is useless for Glowforge. But, everything they discuss prior to activating their extension is still useful. Instead of using their extension, you just run a Save As and choose SVG for file type.
Built in with Inkscape (.91 and later) are some laser centered extensions. These are found in Extensions->Render.
Gear and Hershey Text are the ones I know of as being laser oriented. I thought there was one for a tab and slot box generation, but don’t see that off hand.
Gear is aptly named. Generates gears. Hershey Text makes text in a limited range of fonts, but text which is designed for a laser to trace the outline only. Most normal text fonts will result in a raster type cut from the laser by default.