You can use something like this to read license file to memory:

int ReadBinaryFile(char *filename, unsigned char **licData)
{
        long fsize = 0;
        FILE * fp;
        fp = fopen(filename,"rb");
        if(fp==NULL)
        return -1;

        fseek(fp,0,SEEK_END);
        fsize = ftell(fp);
        fseek(fp,0,SEEK_SET);

       *licData=(unsigned char *)malloc(fsize);
        fread(*licData,sizeof(unsigned char), fsize,fp);

        fclose(fp);
        return fsize;
}

and now you can use this to initialize IDKit:

unsigned char *licData=NULL;
int licLength = ReadBinaryFile("iengine.lic", &licData);
IEngine_InitWithLicense(licData,licLength)