Definition:

emacs20-dl: The GNU Emacs editor. (Dynamic Loading supported) GNU Emacs is the extensible self-documenting text editor. This binary supports the Dynamic Loading architecture(dl). If you want to use dynamic loadable modules, you should use this instead of pure emacs20 package. Dynamic Loadable Module examples are Canna/Wnn input method support. (emacs-dl-canna/ emacs-dl-wnn package) And some dirty patch applied.

Dirty means such as, Rejected by upstream authors (difficult for merge), Code from other emacsen, like XEmacs/Meadow/obsolete Mule2.3, or backported. From Debian 3.0r0 APT

* Linux/Unix/Computing Glossary