The meaning of "but as many as received him"

[NewHopeR]

Does "But as many as received him" mean "but to all who received him"? If so, I wonder the grammatical structure of the former. Why the former can be equivalent to the latter?

Context:

"But as many as received him, to them gave he power to become the sons of God, even to them that believe on his name." John 1:12

[Raymott]

There is controversy among Christians as to the exact meaning of this text. I read "But" to mean "Only". Then, the text would read, "Only to those who received him...". Remember that this text is from the 16th Century and that meanings and usage has changed over the years.

What's the controversy. Don't they mean the same thing (in this context) - "Any of/all/only those who received him ..."
"If they received him, he gave them power. If they didn't, he didn't." Is there a theological issue hanging on the meaning?