ppl was created to address the need for a decentralized address book storage system. There are a lot of different contact details storage solutions out there and they all have their own strengths. What was lacking was one that I felt I could count on to entrust with the "master copy" of all the disparate contact information I possess.
It's also intended to address the apparent lack of a proper CLI address book. There are people who enjoy the conversational nature of CLI interaction. You ask "Whose birthdays are coming up soon?", the computer answers immediately, and your interaction with the software is over with no further requirements that you close a window or slide a widget.
Why the CLI?
The command-line is a good fit for address book software because data about contacts is usually 100% plain text. It also works well because a given user interaction with an address book typically consists of one short operation: reading or writing a single piece of data. And since we normally want to keep our address book data for our entire lives, the command-line's immunity to the shifting sands of GUI toolkits and discontinued SaaS products is a big plus.
ppl uses git as its storage backend. Git's decentralised approach really suits this usage as it allows continued read/write access to the address book in the face of network downtime and cloud outages. And because git never destroys data, no botched sync attempt can permanently wipe an entire address book by accident.
This software was conceived and created by me, Henry Smith, some guy who likes writing code. I care about software quality, and I often prefer to use the CLI for tasks involving just plain text.
According to the project's git logs, work on ppl first began on November 10th 2012. Apparently I had nothing more exciting to be doing at 11pm on a Saturday night.