SELECT 
  lang.name, 
  IF(
    cscart_ult_language_values.value IS NULL, 
    lang.value, cscart_ult_language_values.value
  ) as value 
FROM 
  cscart_language_values lang 
  LEFT JOIN cscart_ult_language_values ON cscart_ult_language_values.name = lang.name 
  AND company_id = 1 
  AND cscart_ult_language_values.lang_code = lang.lang_code 
WHERE 
  lang.lang_code = 'en' 
  AND lang.name IN (
    'powered_by', 'copyright_shopping_cart', 
    'powered_by', 'copyright_shopping_cart'
  )

Query time 0.00032

Explain
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE cscart_ult_language_values system PRIMARY 0 const row not found
1 SIMPLE lang range PRIMARY PRIMARY 392 2 Using index condition

Result

name value
copyright_shopping_cart [product] - Shopping Cart Software
powered_by Powered by