Hi,
I noticed some kind of mirror content at sqlite.org. 

For example
  https://www.sqlite.org/index.html
is identical to
  https://www.sqlite.org/matrix/

The confusion starts when search engines currently index both often offering the results as different entries. Try googling [sqlite download] for example. 

Is this some kind of ongoing migration? If so, maybe it's better to forbid one of them with robots.txt? 

Thanks

Max