Actually, you don't need to sink any investment into a commercial ecosystem here!
plotly.py and the plotly.js rendering library are both MIT licensed, developed in the open on GitHub, and totally self-contained.
Everything in the technology stack used in the announcement post is free, open source, self-contained, usable offline, and doesn't require an account. The plot.ly cloud integration is totally optional.
Re:Introducing plotly.py 3.0.0
by jjoonathan on Thursday July 05, 2018 @04:42PM
(#17466661)
Cool! I'll have to give it a look then!
It's completely open and that's amazing. The ability to design plot.ly plots offline in a jupyter notebook and easily deploy it to our reporting website (Using Dash) is so quick and easy. Even the default interactive elements is plenty for most use cases.
Obviously python itself is open, I mean the API :-)