1. Doctors Without Borders help many sick people in poor countries.
2. Doctors Without Borders helps many sick people in poor countries.
(Do I have to use 'help' or' helps'? Which one is correct?)
In this case, "Doctors Without Borders" is the name of an organization, and should be treated gramatically as a singular proper noun, even though the words 'Borders' and 'Doctors' are both plural. #2 is correct.
The French and international name of the organization is "Médecins Sans Frontières" or just "MSF".
See www.doctorswithoutborders-usa.org
for the use of the organization name as a singular noun.