[Updated Oct 16] Join the World of Warcraft: Forever Stress Test
Updated Oct 16: Blizzard moved the open Stress Test from Oct 19 to Oct 21. Anyone can join WoW: Forever with no sub, game time, invite, or beta access. Local windows are NA 2:00 p.m. PDT, EU 19:00 CEST, KR 06:00 KST Oct 22, TW 05:00 CST Oct 22. Beta goes offline shortly before and should return after, and the window may end early or run late. Join via the Battle.net "WoW: Forever Stress Test" option under In Development. Stress Test characters are wiped afterward, ahead of name reservations opening Oct 27.
Source: Blizzard Entertainment, worldofwarcraft.blizzard.com