Final answer:
Debian is recognized for its stability, security, and customizability, and officially includes free software; hence, the answer is 'All of the above'.
Step-by-step explanation:
Debian is known for prioritizing several aspects, but it officially includes free software. Among the options given, Debian is especially renowned for its stability. However, the Debian community also values security and provides users with the ability to customize their system extensively. Thus, the correct answer is 4) All of the above.