I am not aware of any official translation project for Slackware, but quite a few of the components that jointly make up Slackware are translateable, such as KDE and a majority of the GNU utilities.
If you set the correct locale for Malayalam in /etc/profile.d/lang.sh and also select that language in KDE, you should be at least on your way...
Having said that, this all depends on how much has previously been done on the translation side in for instance KDE - you might want to have a look at
http://l10n.kde.org/ to see how far they've come there...
As for the Slackware specifics such as the pkgtools etc, I believe they are hardcoded English only...
-y1
