During a Podcast with StadiaCast John Justice has said that the Buddy Pass for Stadia will be coming out within two weeks.  The 6 months in the small print as well expected was a just in case scenario.  The Buddy Pass comes with the Founders Edition of Stadia and allows a friend access to Stadia for 3 months without having to buy the Founders Edition.

 

You can watch the full StadiaCast Podcast below.