Hi James, by "converting" do you mean setting up the C SDK in other IDE such as Eclipse? there is a C/C++ tooling available for Eclipse you might want to try this : Eclipse CDT
I think this is working quite well for C++ projects from my past experience, although I have not tried the C SDK from Thingworx yet with this tooling in Eclipse. Would be interesting to hear from you, if you do plan to work on this.
Hope this helps.