Posts: 3,283
Threads: 104
Joined: Jul 2005
Let me explain:
The SDK sources require the expensive IAR compiler for building the flash file and the somewhat less expensive Visual Studio to build the emulator. Visual C/C++ Express isn't sufficient because it lacks the MFC libraries the GUI is based on. This made me update the the emulator part so that it can be compiled separately from the rest of the software and encapsulated the GUI in a DLL. There are not many situations that require an update to this DLL (which still requires the paid version of Visual Studio). Most changes are to the calculator sources and these do not depend on features not available in the free Express edition. The flash file is completely built with the free GNU tools.
If you want to create your own software you better base it on the WP 34S sources.