Update README.md

Author: jackparmer

Diff for: README.md

@@ -24,7 +24,7 @@ See the [Python documentation](https://plot.ly/python/) for more examples.
 React about what's new in [plotly.py v3](https://medium.com/@plotlygraphs/introducing-plotly-py-3-0-0-7bb1333f69c6)
 
 ## Overview
-[plotly.py](https://plot.ly/d3-js-for-python-and-pandas-charts/) is an interactive, browser-based graphing library for Python :sparkles:
+[plotly.py](https://plot.ly/d3-js-for-python-and-pandas-charts/) is an interactive, open-source, and browser-based graphing library for Python :sparkles:
 
 Built on top of [plotly.js](https://github.com/plotly/plotly.js), `plotly.py` is a high-level, declarative charting library. plotly.js ships with over 30 chart types, including scientific charts, 3D graphs, statistical charts, SVG maps, financial charts, and more.