This handy plugin causes new orders in your store to be automatically and instantly sent to your printer. Save time and money, and fulfill orders faster! Orders, invoices and packing slips/delivery notes can be printed. Compatible with any printer (including thermal), or with saving a PDF to Google Drive. No more logging in to find orders; no more time spent printing off delivery instructions; no more delay in between orders being placed and being able to fulfill them.
I thought the plugin was under GPL, but a closer inspection shows that the libraries it uses are LGPL and MIT. The author doesn’t disclose any more information on other dependencies, so as you say, it might not be licensed under GPL.
I made a donation to the site anyway, thanks for keeping everything updated.