It would be interesting for all of us if those who have used Leto DB share here theirs impressions, positive points, improved performance, problems, etc.
But that was back in 2010, it may have greatly evolved in this time. Knowing Alexander Kressin as I know him (he helped a lot when we started building Harbour: he wrote the DBFNTX RDD, the first preprocessor (though lately Przemek, replaced it), and helped on so much more areas) I am sure that Leto DB must be much better now than back in 2010.
Leto is a multiplatform database server or a database management system, chiefly intended for client programs, written on Harbour, be able to work with dbf/cdx files, located on a remote server.