hi.
uhh. i just noticed a php notice in the xml. not good. Must have changed something of my hosting 
yes. the numbers are an auto_increment in the database. so they just count up.
the category tag was planned for a category selection in the application. Currently it is only possible to select the category on the webversion code-i.de.
For the ardulibrary application it is not used at the moment.
Now. the authors are not used in the application either. But they should show the author of the library.
"sascha" is my name.
But i am not the author of the libraries. i just added them in my application.
now. You are right about the missing link for a documentation. I did it the way that it opens a url with the id of the library. So if you double-click on a library it opens for example code-i.de
mh. as you tell it. I fear i hardcoded that link. Need to change this for sure.
if you need some change to the xml it should not be a problem and i will implement it.
Hope i could help.
//Edit: yes. i had this version problem too because many library developers use some odd way of versioning or do not write any version at all. So i think the best way is to numerate them?