FTGL is used for font rendering and FTGL uses the FreeType library for fonts. ...

FTGL is used for font rendering and FTGL uses the FreeType library for fonts.  FTGL contains a header file named FTGlyph.h and FreeType contains a header file named ftglyph.h and they are the same name but differ only in capitalization.  The Apple Mac file system is case insensitive and this name clash results in compilation problems on Mac OS X 10.10 Yosemite.  FTGL FTGlyph.h has been renamed to FTGLGlyph.h to fix this problem as described in http://sourceforge.net/p/ftgl/bugs/41/.   Also note that FreeType's ftglyph.h is not used directly but is defined with the macro FT_GLYPH_H.