I've already implemented the server side for Slax buildscripts. You may try to explore the 'slax' command, no changes at Slax side necessary. I will be happy if you test this all to see if there are any bugs. You should always start by downloading of a template buildscript, use command:
$ slax buildscript download template
Then edit this template to suit your needs. Run it to produce your slax bundle. Uploading and downloading of your own buildscripts work as well, so when you are done editing, you may share it with others by:
$ slax buildscript upload YOURSCRIPT.SlaxBuild
You can also try commands "slax search KEYWORD" and "slax info NAME". For example the following command will list you all available localizations:
$ slax search localization
Your uploaded scripts will be just stored on the server now, the 'autobuilding' process DOES NOT WORK YET neither activation of remote module, it will be implemented later, I hope tomorrow, because then I will be off for 4 days due to my wife's plans to go away for the entire weekend (while weekend starts on Thursday evening) and I'll stay alone with our kids; I don't want them to watch TV all the day so it's better to go offline :)
I've supplied buildscripts for all Slackware packages to the repository and I've became their maintainer. Feel free to test and report in case of any errors.
How to use this practically
You can use this all in practice already. For example if you wish to use perl, which is not included in Slax by default, issue the following sequence of commands to get it built and activated:
$ slax buildscript download perl
$ sh perl.SlaxBuild
$ slax activate perl.sb
$ perl -v # just to see it's there!