Those who purchased All Access passes to recent events like GDC already have full access to GDC Vault, and interested parties can apply for the individual subscription via a GDC Vault subscription page.
In this 2017 GDC talk, Kole Hicks & Chris Hunt share the details behind crafting the music and sound for the gritty, unforgiving, and indifferent world of Kenshi.
Finally, current subscribers with access issues can contact GDC Vault technical support.
Group subscriptions are also available: game-related schools and development studios who sign up for GDC Vault Studio Subscriptions can receive access for their entire office or company by contacting staff via the GDC Vault group subscription page.