Calc is the spreadsheet component of the LibreOffice office suite. (LGPL)
Linux - FreeBSD - Windows - MAC OS X
Gnumeric is a free spreadsheet program that is part of the GNOME desktop. (GPL)
Linux - FreeBSD - Windows
Calligra Sheets is a fully-featured spreadsheet application. Use it to quickly create spreadsheets with formulas and charts, to calculate and organize your data. (LGPL)
Linux - FreeBSD
3 applications