make looks for [Mm]akefile if you run it with no arguments, but here it's being run recursively (or included). On OSX, filenames are case-insensitive, which could be a possible reason why it works for some people. On Linux, filenames are case sensitive.
That seems to be the case, since running file on one of the existing .o files says that they are Mach-O i386 objects. The readme doesn't mention OS X though, only Ubuntu
