Hi @JohnP
The equivalent of #include <Arduino.h> is to do #include "application.h" but you usually don’t need to in your main sketch. That name is very likely to change in the near future so I don’t think it has been doc’ed. If you add a C++ library to the web IDE (there’s a little circle plus up near the top) then you should have the include in the C++ header file, but the Particle pre-processor does it for you in you sketch (.ino file). So users of libraries don’t need to know about the include, but authors of libraries do.
The application include brings a lot of the Wiring language you are familiar with already and that is listed in the firmware section of the doc.
The boolean datatype is called bool like C and C++. You can #define boolean bool I guess but fixing the library to use the standard C/C++ datatype is probably better.