What are some alternatives?
When comparing dhtmlxSpreadsheet and Excel Online, you can also consider the following products
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.
Google Sheets - Synchronizing, online-based word processor, part of Google Drive.
Microsoft Office Excel - Microsoft Office Excel is a commercial spreadsheet application.
TableEdit - free mac app to view and edit spreadsheets
EtherCalc - EtherCalc is a web spreadsheet.
LibreOffice - Calc - LibreOffice Calc is the spreadsheet program you've always needed. A fork of OpenOffice.