The Use of USPTO 'Continuation' Applications in the Patenting of Software : Implications for Free and Open Source

This paper examines the role played by "continuations" (procedural revisions of patent applications) within software patenting and the implications that the use by patentees of continuations has for free and open-source software design. Our research analyzes data on continuations in software patenting 1987-99, providing information on the effects of changes made to the U.S. patent laws in 1995 intended to curb "submarine patenting." Our analysis of all U.S. patents issued 1987-99 shows that the use of continuations grew steadily in overall U.S. patenting through 1995, with particularly rapid growth in continuations in software patenting. Sharp reversals in these growth rates after 1995 suggest that changes in the U.S. patent law were effective. We analyze the role of continuation patents in creating opportunities for patentees to engage in strategic "hold-up" of software adopters and follow-on software innovators, and extend the analysis to open-source software