A. You all probably mean mod_rewrite and not .htaccess. You happen to use it in .htaccess but its still mod_rewrite (can be placed in httpd.conf as well)
which leads to foe's remark
Why do you think you can do anything with script that you cant do with mod_rewrite????
mod_rewrite blocks most of hotlinking (if used right) and not only 50%. What you do to block hotlinking is block all access to images (jpg,gif,...) from HTTP_REFERER that is not your own site.
(problem with anti-hotlinking is that it may block more than 100%
meaning blocking legal requests from client browsers that hide HTTP_REFERER [personal firewalls and shit])
Id be happy to know what a script can do that mod_rewrite cant regarding the hotlinking issue. foe? enlighten us, would you?