Conversation so far:
What genre of music were Rhett and Link involved in?
Rhett & Link perform live musical comedy.
Did Rhett & Link ever release an album?
Rhett and Link have completed two albums.
Are there any other interesting aspects about Rhett & Link's music besides performing live musical comedy and completing two albums?
In 2005, Rhett & Link independently released I’m Sorry, What Was That? (Live in the Living Room), a live album featuring The Wal-Mart Song“
Did Rhett & Link ever perform anything from their albums live?
On May 16, 2017 Rhett & Link announced they would be going on tour around the United States in order to promote their upcoming book, performing around the country.
Did Rhett and Link have any albums after 2015?
To correspond with their YouTube Red show, Rhett and Link's Buddy System, the duo released the album Buddy System (Music From Season 1) which includes seven songs.

Question: When did they release this album?
Self-contained rewrite: When did Rhett & Link release Buddy System?