<introduction> Hi, I'm Hugh Wimberly, and I submitted a proposal for SoC. I was directed here to ask questions, and hope I'm not bothering anyone.</introduction> For my project, I proposed to extend the regex library to use DFA-based regular expression matching, and essentially make it a hybrid matching engine that would be more predictably time-bounded. One of the reasons I proposed such an undertaking was that I know that there are other implementations that use this model; Plan 9 uses DFA-only regular expression matching, Tcl uses a very advanced hybrid model, and GNU awk uses almost exactly the model I proposed. These (and other) implementations are in general written in C and are all open-source. Since they're written in C, I couldn't directly use code anyway, but I'm a little worried about how much I can use them as a reference since most of them are licensed under the GPL, and Boost has an incredibly open license that isn't compatible with the GPL. My question is really just "what counts as using the code"--does writing similar code, knowingly using it as a reference infringe on copyright? If it does, I think I have to amend my proposal, because I think it would take me much longer than I thought if I can't reference existing implementations. -Hugh