It would be nice, if FTGL had a possibility to determine the library version at runtime.
This could be done either with a function call (like OpenGL's glGetString) or by defining some macros (#define FTGL_MAJOR_VERSION 2, ...).
The next release will feature an FTGL::GetString() C++ function, and an ftgpGetString() C equivalent.
That's ftglGetString(), not ftgpGetString().
Also note that this function will not be backwards-compatible, as previous versions did not provide it.