According to wikipedia, "In the United States, under current patent law, for patents filed on or after June 8, 1995, the term of the patent is 20 years from the earliest claimed filing date. For patents filed prior to June 8, 1995, the term of patent is either 20 years from the earliest claimed filing date or 17 years from the issue date, whichever is longer." so, the answer is...when was the patent granted.

Getting a patent does not make the algorithm secret. In fact, it does just the opposite. The paperwork that was filed becomes public record so everyone can see how you do something. The patent grants you the right to exclude others from making or using your design.

See http://en.wikipedia.org/wiki/Patent

>Is Rushmore patented? If so, when does it run out? If not, what's to prevent someone from making a VFP clone or creating, at least, a similar data engine for their programming language? Some of the internals of Rushmore are known. For instance, it's based on B-Trees, but goes further and eeks out more speed with additional techniques. There have been one or two articles in FoxTalk and/or FoxPro Advisor on it that explain some things with more detail. Of course, the answer might be "why bother" - just use MySQL or something else like Oracle or SQL Server. Valid response, of course. But local tables have proved their worth over the years. Why not continue to have both options? (Which we will via VFP for a good while, but . . .)
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>Russell Campbell