@amoroso What Quicklisp calls a distribution is a package catalog. There's always Quicklisp's built-in one. Ultralisp is a second one. You can add any number of such distributiions as you like.
The real question is what happens if a package is in multiple distributions, in different versions. There is a largely undocumented priority mechanism for deciding that. If you install Quicklisp and Ultralisp from their respective instructions, Ultralisp takes precedence.