It can be used to build the infrastructure of distributed Web applications that do not depend on third-party services such as Google Docs and others.
Can be integrated into the online business applications.
Auto plug-in - Daniel Bricklin, who is known as the "father of spreadsheets."
He invented (invented) and implemented the world's first spreadsheet in 1979 (!) Year. It was the VisiCalc software for desktop computers Apple.
Today, the same Daniel, puts on his githabe source browser-based spreadsheet.
Backend is written in Perl, but I think can be integrated with any server-side language.
This is a real spreadsheet: this example uses JS scripts to 23,700 lines (this is not a compressed source, easy to develop).