Is Metasploitable already inlcuding in Kali or do I need to download it?

[Make Kali Great Again]

Is Metasploitable already including in Kali or do I need to download it?
Is it meant to be run side by side with Kali open?
Should I use the official site for the download or Source forge if my os is debian?
I am on Debian which one should I pick from the official site https://apt.metasploit.com/