Cyanogen is now part of Android history making it in Wikipedia.
“There exists a thriving community of open-source enthusiasts that build and share android-based firmware with a number of customizations and additional features, such as FLAC Lossless audio support and the ability to store downloaded apps on the microSD card.
Those firmware packages are updated frequently, incorporate elements of Android functionality that haven’t yet been officially released within a carrier-sanctioned firmware, and tend not to have arbitrary limitations. CyanogenMod is one such firmware.
On the 24 September 2009 Google issued a cease and desist letter on the modder Cyanogen, citing issues with the re-distribution of Google’s closed source applications within the custom firmware. Even though Android OS is open source, phones come packaged with closed-source Google applications for functionality such as the application store and GPS navigation. Google has asserted that these apps can only be provided through approved distribution channels by licensed distributors. Cyanogen is complying with Google’s wishes and will continue to distribute his mod with alternative, open-source applications. He will provide a method to install Google applications for those who own them.”
Pros can dispense fear of.