From the announcement:
The Brood have been evolving and genetically reincarnating for centuries, and the rapid escalation of Samarian conflicts in the last few decades has caused the most change in them to be sure. With the promise of a new Dark Age: Brood faction-focused book planned for later 2018, it was decided that we would give the age old Brood faction a rules-facelift before their full new release. Now, as of today, the gaming populace of Dark Age players and fans get to use these new rules officially.
These new rules are technically a BETA of the final rules that will be used to help create those released in the 2018 book and faction card pack (along with many other new toys!). This means that, while we believe these rules to be fair and competitive in their current state, we accept that it might need a little spit and polish here and there. This official beta release gives you, the fan base, a chance to chime in and tell the development team about your experiences with these Brood rules before they go into final print next year. For those wishing to make such notes or comments, please email email@example.com with “Brood Beta Rules Notes” as the subject line.