This is a rudimentary breakdown of how level files are formatted for the game Jetpack by AdpetSoftware.
Note that the term "JetSCII" used throughout this document is not an official term and is simply a placeholder for a subset of ASCII characters supported by Jetpack level file names.
Adam Pedersen said the following on the official Jetpack Discord server:
I hereby grant anyone the right to make a Jetpack-inspired game, including use of all assets (graphics, audio, and levels), as long as it provides clear attribution to the original, and acknowledges that all intellectual property rights remain with Adept Software. For example, "Inspired by Jetpack by Adept Software", with link to adeptsoftware.com