It is good publicity and good will to release open source code.
They still have their business advantage intact: they have the data and the awesome infrastructure.
It seems like a lot of big companies are open sourcing their deep learning stuff. Part of me wonders if they do it because, as people get scared of AI, the federal govt can't come after lots of of small companies using the opensource AI to regulate/fine/shutdown. They could come after just Google or FB once people start loosing lots of jobs to AI, if they where the only kids on the playground.
They are mostly releasing their tools though. The raw diamonds are the trained network weights, it's architecture and the data itself. Releases on those parts we see rarely from private companies.