Welcome to DLG Professional
DLG Professional is the “Bulletin Board Operating System” for the Commodore Amiga. DLG provides the software tools and environment necessary to create a flexible electronic bulletin board system.

What is DLG?
The disk operating system (AmigaDOS) of your Amiga consists of a number of commands which are loaded into memory and executed when needed. Each command performs a specific task - copying afile, playing a sound, displaying a picture, and so on. DLG is very similar to AmigaDOS in concept. We took all of the various tasks performed by a bulletin board system and broke them down into small programs, each of which performs a specific task. DLG's commands include those that write messages, send files, perform maintenance, and so on. Like AmigaDOS, DLG supports batch files (lists of commands to execute in sequence), command line arguments, etc.

You can find additional information about DLG here, and you can try out a DLG BBS here. Here's a link to the official announcement of DLG being open-sourced and the software.  Here's a link to a really good source of DLG add-ons and related utilities.