avoiding the need for logins in the Physics Derivation Graph website

Now that the PDG interface is a webpage, and users (not just developers) are the audience, there is a question of whether users of the website need accounts.

User accounts

Having an account would enable persistence of data specific to one user.
Downsides:

• Password management and security
• user account shenanigans
• 
  

No users accounts

Live use without an account, modeled after services like https://repl.it/  and https://www.onlinecharttool.com/graph, enable users to explore the capabilities without need for registering and creating a password.

Data could be uploaded and download

Source code

Historically the Physics Derivation Graph was developed on the command line using bash and Python. This implied a single user.
The source code was available, so other developers could pull a local copy to make edits.

API calls

This would allow interfaces to be developed that are independent of the backend.