On Tue, 18 Dec 2007 19:24:26 -0600 (CST), "Mike Miller"
<mbmiller at taxa.epi.umn.edu> said: 
> Why can't I use four different package systems on the same installation
> of 
> one distro?  The reason isn't philosophical -- there is either a
> technical 
> reason why I can't do it, or I can do it.  The distro might come with
> only 
> one package management program, but they are all freely available so I 
> ought to be able to compile them all and use them all, if I want to.


The reason is one of practicality and it's that you can only use a
package management system that supports the package format you want to
use.
For practical reasons, you can't, to a large extend, use different
package formats especially when you're dealing with package
dependencies.
The reason I say "practical" is because technically, you can use
different package formats as song as you configure the software so that
dependencies are satisfied, and, for scalability, invent another piece
of software that can manage those dependencies based on the two
different package formats.