why db42 db44 and db48 ?
 

what reason is to have 3 versions of same package on systema ?

Other distros ships only one ,

why slackware haver 3 ?

The db42 and db44 packages both provide libraries that are included in the aaa_elflibs package.
Maintaining older libraries provides stability, in case other compiled packages require them. http://www.linuxquestions.org/questi...ml#post4761353