Suppose there is a software written in a language A and covered by "BSD license", now if I rewrite the code in another language B and create a software without acknowledging the original software, am I violating the BSD license?
Wherever you use somebody else's work, that contribution should be acknowledged. Whether translating code in this way violates the word of the BSD agreement may be debatable, but the fact remains that you would be using work originally created by another, and this should be duly acknowledged.
To present another person's work as your own would be plagiarism, so - at the very least - your translated software should include an explanatory note referencing the original software and acknowledging the authors. If you don't want to reference somebody else's code, then you could just write your own - original - version from scratch.
Wherever you use somebody else's work, that contribution should be acknowledged. Whether translating code in this way violates the word of the BSD agreement may be debatable, but the fact remains that you would be using work originally created by another, and this should be duly acknowledged.
To present another person's work as your own would be plagiarism, so - at the very least - your translated software should include an explanatory note referencing the original software and acknowledging the authors. If you don't want to reference somebody else's code, then you could just write your own - original - version from scratch.
Translation any thing even a book from one language to other needs a permission from the author. The acknowledgment without the permission is not enough and is duly. So you should contact the authorized company owns that software and ask for a permission otherwise you violate the property rights.
As Paul Barrows states, since all you are doing is translating the code from language A to language B, presenting it as your own is both plagiarism and dishonest.
You should acknowledge that the code came from BSD by using the required copyright statement as a comment in your translated code and specifically mention it during any presentation(s) you make based on your translated code.