Zone files then what?

[csmaster2005]

ok guys,
I have had zone file access for a while, and planned on running whois on each domain so I can get info on them such as expiration date....
But I see that there is no bulk whois license or anything of that nature? If I run whois on them, I am sure the server ip will be blacklisted.
My question is, how do other sites like whois.sc get expiration dates of every domain?
How do sites make drop lists?

If anyone has any comments to the above, please provide :P

 

[.edu]

Everything u are looking for is in the zone file. You will need to use your own knowledge to mine that data.

 

[csmaster2005]

the zone files only have the domain and it's nameservers, how would I get the expiration date, etc from it?