What are some alternatives?
When comparing Gnumeric and SpreadsheetWEB, you can also consider the following products
LibreOffice - Calc - LibreOffice Calc is the spreadsheet program you've always needed. A fork of OpenOffice.
SpreadsheetConverter.com - Use online spreadsheets, smart forms and beautiful charts in your blog or website. Put your booking and order forms online. Show live charts. Change any cell and the online spreadsheet or live chart immediately updates itself.
Microsoft Office Excel - Microsoft Office Excel is a commercial spreadsheet application.
Publisheet - Publish your Excel sheets to the web as dynamic web applications with formula support.
Google Sheets - Synchronizing, online-based word processor, part of Google Drive.
Appizy - Convert spreadsheet to web application