If anyone is interested in developing content for the White Lies RPG (or converting material they've published for the Covert Ops RPG to White Lies, to reach another group of gamers), please use one of the following compatibility logos on your products. It'll help with recognition and avoid any confusion over the different espionage offerings.
I'm not personally very picky about licensing, but you should consider adding the OGL to the end of your product (even if it's a freely distributed one) and customizing the area at the top (product identity) and the bottom (trademark/copyright identification). It only takes a couple minutes to do, and makes those people who find it important happy. :-)
We don't have any special guidelines for creation of product. It's an OSR product so feel free to customize, modify, offer alternatives to the main rules, add classes, organizations, enemies, new creatures, whatever your heart desires.
You can grab a copy of the Open Game License version 1A to customize for your product below: