The open source softwares are different from the proprietary s/ws not only inprice but it makes the user of the software feel as a real user of the software both for programmers and also for the normal users of the software by using the freedoms.
All the opensource softwares are licensed under GNU- GPL which are based on the COPY-LEFT concept while proprietary software are base don copyright concept .
Here are some TOP alternatives to the top proprietary s/w :
Proprietary Vs OpenSource
Operating System
* Windows Vista Vs Ubuntu Linux
* Windows Server Vs RedHat/Suse Linux
Internet Browser
* Internet explorer Vs Firefox
Database
* Microsoft Sql Server Vs My Sql
Office
* Microsoft Office Vs Openoffice
* Mactopia Vs Neooffice (FOR MAC OS)
Office Tools
* MathWorks MATLAB Vs Scilab
* Microsoft Access Vs Kexi
* Microsoft Word Vs OpenOffice Writer
* Microsoft Excel Vs OpenOffice Calc
* Microsoft Visio Vs Dia
Productivity
* Blackboard Vs Moodle
Graphic Programs
* Adobe Illustrator Vs Inkscape
* Adobe PhotoShop Vs GIMP
* Adobe Premiere Vs Avidemux
* AutoCAD Vs Archimedes
* Microsoft PowerPoint Vs OpenOffice Impress
* Microsoft Paint Vs Tux Paint
* TruSpace Vs Blender
Web Editors
* Adobe GoLive CS2 Vs Mozilla SeaMonkey
* Adobe Dreamweaver Vs NVU
* Macromedia Flash Professional Vs OpenLaszlo
* Microsoft FrontPage Vs Bluefish
* Windows Notepad to ConTEXT
* Altova XMLSpy Vs XML Copy Editor
Publishing
* Adobe Acrobat Vs PDFCreator
* Adobe Framemaker Vs DocBook
* Microsoft Publisher Vs Scribus
Communications
* AIM Vs Pidgin
* FeedDemon Vs RSS Bandit
* Microsoft MSN Messenger Vs aMSN
* Microsoft Outlook Vs Thunderbird
* Skype Vs Wengophone
Media
* iTunes Vs Songbird
* Nero Burning Rom Vs K3b
* Quicktime Vs Darwin Streaming Server
* TiVo Desktop Vs Galleon.tv
* Windows Media Player Vs Miro
Utilities
* CuteFTP Vs Filezilla
* iBackup Vs ZManda
* Norton Ghost Vs Partition Image
* Rational Purify Vs Valgrind
* WinZip Vs 7-Zip
Security
* Kaspersky Anti-Virus Personal Vs Winpooch
* McAfee VirusScan Vs ClamWin
* Norton Personal Firewall Vs WIPFW
Financial
* Authorize.net Vs OpenSSL
* Microsoft Money (Plus) Vs TurboCash:
* Quickbooks Vs Compiere