"Its clone" -- what clone?! Spanner has only barely been announced. It's incredibly premature for an article to start making claims about a "clone" of Spanner, when we haven't even seen anything about Spanner yet beyond marketing information.
CockroachDB is referred to as the clone here. They once gave a talk literally titled "Towards an Open-Source Spanner" (https://www.youtube.com/watch?v=ndKj77VW2eM), so I don't believe that's an unfair characterization.
The Spanner paper was published in 2012 on the Google Research site. It describes the entire system. We know a lot about the internals beyond marketing information.
Spanner was announced in 2012; Cloud Spanner was announced this week. The clone is CockroachDB and has been in the works for a few years.
Wow, OK. The article didn't make that part very clear at all -- I assumed they were talking about a hypothetical future clone, not one that already existed. :/
It's CockroachDB. The guys who created Spanner just left (the clone) called Cockroach Labs.