Warhammer Community has posted that the GSC rules for Necromunda: Underhive have been updated and now available as a PDF. There are some changes to the fighter types, different Wyrd powers and other small updates.
Back in the misty depths of March (aeons ago in Warhammer time), our pals at White Dwarf released a set of rules for using Genestealer Cults Gangs in Necromunda. With March’s White Dwarf being currently inaccessible for those not in possession of a time machine, we’re making them available once more, for free, and enshrined forever in the form of a nifty PDF download
You can download the new PDF here from Games Workshop and we'll make it available in the YakTribe Vault for archival purposes.