[striking]

Oracle, Microsoft. They're called "DeWitt clauses", after the researcher who first invoked Oracle's wrath after publishing benchmarks and finding them to be the slowest. Read on:

* more about DeWitt: https://en.wikipedia.org/wiki/David_DeWitt#The_%22DeWitt_Cla...

* an overview of database licenses with such a clause today: https://stackoverflow.com/a/12116865/1376005

* an essay discussing the legality of such clauses, with links to further material on/about them: https://www.dwheeler.com/essays/dewitt-clause.html