What is the meaning of this calligraphy?
As far as I am concerned ,this motto is related from Lunyu which from China not from Korea . It is written by Chinese Confusius and his disciples. It's original motto is '君子周而不比，小人比而不周'. I think it is exactly similar to the motto you provide. 


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'周'means : coordinate;harmonize 
[That is to say the person who can in charge or  organize his members perfectly , and he can lead the team on a good way,do the good things.]
'比'means:  collude;gang with somebody  

That is to say,the motto want to tell us, the difference between 君子 and 小人 is whether he has the quality of benevolence. A person of noble character emphasize morality and justice,while 小人 only pay attention to benefit.