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Is React a core Facebook asset? Where is Facebook sharing their ad tech? That’s the closest thing Facebook has to a core technology. Even Facebook’s ability to technologically scale isn’t that much of a core differentiator. We haven’t really seen a truly competing social network even get to the point where this was a problem. Facebook’s core is, if anything, the (social) network itself, which is something that it DEFINITELY closely protects.

Making their APIs easy to use like they used to be 10 years ago will be equivalent to releasing their core assets. In the past you could do almost anything from the Facebook API that you could do with their web or mobile app.

They release a lot of open source stuff as other commenters have mentioned but you can't build a Facebook or Instagram competitor just by integrating those components.

Their core asset is targeted advertising on their social network, none of that is any open, and that's what the GP means.

And OpenCompute