With some limitations I released application in VFP8 which used Phdbase in 2003 and it is still alive being maintained by other company. There was one table there with more than million records dynamically re-indexed during updates without problem. Known limitations applied to earlier versions ( e.g. no spaces in folder names, no long names for cursors ) . In fact, I had a lot of problems with dynamic re-indexing in VFP5 which went away in VFP6.
I wouldn't recommend to anyone to use this very old black box ( last version 3.61 released in 1997 ) , as I solved all free text search problems in my case using Lucene.Net ( open source ) with VFP application.
The reason I started this thread is that I always wanted to see a source code of Phdbase and asked many times to sell it ( without any response). I am still interested now to browse it ( though found a viable alternative ) , but looks like this source code is never going to materialize.

>As far as I know, it doesn't work with any version after VFP6.
>
>>Does PhDbase work in VFP9 if you do the SET ENGINEBEHAVIOR 70 or SET ENGINEBEHAVIOR 80 command?
>>