If you're unfamiliar with iBoot and SecureROM, let me explain it briefly: Those components are responsible for booting the device and ensuring security, just as their names imply. You can roughly call it a bootloader and a "Secure Boot" for iOS. iBoot ensures iOS is booted and SecureROM ensures that neither iBoot, the kernel or iOS is modified.
In a recent leak, the source code for some parts of iBoot and SecureROM were leaked which makes it unofficially open source. The code was part of an iOS 9 build, which may sound disheartening to people who are hopping for a modern jailbreak to materialise from this, however, it's not bad news. Quite the opposite.
The leak, although for an older version of iOS, is still very valuable and appreciated by the jailbreak community. While the code may not be the latest, the source code of the components may lead to finding new vulnerabilities which are still unfixed in newer iOS versions, and hopefully, permanent jailbreaks for devices which support the build. This would not include the iPhone 7 and newer, but the status of devices like the iPhone 6S and older hasn't been confirmed yet.
If you remember the iPhone 3GS bootloader situation, people always wanted to get their hands on older iPhone 3GS's as those has a fully cracked bootloader which allowed jailbreaks for newer iOS versions, even beta builds, to be released in a matter of hours after the official release by Apple. While the newer iPhone 3GS bootloader has also been cracked now, it is no longer a relevant device which would contribute to modern jailbreak development.
With the source code of iBoot and SecureROM, we could very well see permanent jailbreaks for still relevant devices and even modern iOS versions as pwning those devices could open up upcoming updates.
In short, this is a very bright day for jailbreaking and we might soon see very promising results from this leak, which could even save the jailbreak community from it's slow fade to obscurity.
All we can do now is wait and see what materialises. Meanwhile, why not leave your thoughts in the comments?