Can amcl pack use a map data as a likelihood field? [closed]

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Hi, everyone. I'd to ask some questions about amcl pack and map data.

I've asked a question about a likelihood of a map here.
(http://answers.ros.org/question/49807/likelihood-field-of-map/)

In the above discussion, MAYBE amcl pack uses a map data as binary data(free or occupied).
However, we didn't get solutions for all questions.

Questions are ...

1. Does amcl pack really use a map data in the way?
2. Can amcl pack use a map data as a likelihood field?
   
3. If possible, how should I do ?
4. If impossible, why do you think nav stack apply that way?
   (Without likelihood field, you'll get less robust localization
   because of uncertainty caused by odometry error, sensor noise, inaccurate map data and so on.)
   

You don't need to answer all the questions.
Thanks in advance.