The traditional viewer project has been criticized for being nearly impossible for anyone other than the Lab to get code and bug-fixes into. Pretty much every submitted patch was rewritten afresh by a Lab dev, we're told and only then after many many months.

The new one has a lighter contribution model, allowing direct submissions from users with a very lightweight review process.

Seems to me that the Lab can then cherrypick Snowglobe later for features and fixes that are demonstrated and working.