The glossary was recently made public through a Freedom of Information request by the group MuckRock, which posted the PDF, called "Twitter shorthand," online. Despite its name, this isn't just Twitter slang: As the FBI's Intelligence Research Support Unit explains in the introduction, it's a primer on shorthand used across the Internet, including in "instant messages, Facebook and Myspace."
Yes, that does say Myspace.
The gems above definitely needed to be archived. I'm so glad I now know all the leet internet slang the youth of the internet use!