Your understanding of what occurred in the acquisition is incorrect. (Source: I am a former FoundationDB employee.) Unfortunately I can’t say much more than that.
The VoltDB post is also wrong in many of its particulars, but I’ve gotten into that argument on this site way too many times by now (and last I checked John agreed that some of its claims were overly hasty).
If there’s a particular question about FoundationDB’s performance characteristics that you’re curious about, I can probably give you a straight answer provided that it was once public information.