I read through the entire pitch and I still don't understand what is special about Polar. There are a ton of apps that do all this and more in no particular order:
1) Xodo Reader
2) Liquid Text
3) Margin Notes 3 (AWESOME)
4) KOReader (Open source)
And several dozen more...
1) Xodo Reader 2) Liquid Text 3) Margin Notes 3 (AWESOME) 4) KOReader (Open source) And several dozen more...