Mark this Saturday, September 15th, in your diary. It’s Software Freedom Day and it’s coming to you. That's "free" as in "free lunch" but also "free" as in liberty.

Software Freedom is about more than merely the cost of an item although it is true that most open source software is available at no commercial fee: this happens because the programmers either have altruistic reasons, or have a revenue-raising model based instead on support, customisations, training and other ancillary services.

No, software freedom is about more than this. At its most rudimentary, free software is software that is liberated from constraining licenses. It may be shared with others. It may be installed on multiple computers. More than this, it may be examined. It may be improved. It may be redistributed with the improvements. The software becomes yours to own and to do with as your needs dictate without any fear of violating reams of complex legalese.

But again, there’s more than this. While the above is technically correct, it is the many and varied ramifications that truly define the “free” in software freedom.

Computer programs which are distributed in source-code format are completely transparent. There are no hidden concerns about bundled spyware or adware (or bloatware!). Any worries that the program might act destructively towards competing apps are alleviated.

As an example of the former, one well-publicised case in point is an occasion when Sony’s music label purposely added a rootkit to music CDs; when played on a Microsoft Windows computer, the rootkit was automatically and silently installed and searched the local computer for piracy breaches. This particular application was especially insidious because it actively attempted to mask itself from detection by embedding itself within the operating system. Let’s be clear: nobody objected to Sony fighting piracy or defending its commercial catalogue. However, by the same token, nobody wants unknown software loaded onto their computer, stealing resources.

An example of the latter is easily found among the varied rumours that have found airtime over the years that Internet Explorer and Netscape Navigator, in its heyday, would deliberately sabotage installations of the competing product. Or that Windows Media Player and Real Networks’ Real Player would attempt to harm each other. We’re not saying there was any substance in these oft-repeated allegations; far from it – but the point is the rumours rose and were repeated and found some traction.

Leaving Microsoft alone, perhaps you have found a great new e-mail app online but it comes in compiled .exe form only; what is to say it’s not forwarding your ISP username and password? It doesn’t even necessarily matter if you can not prove that it is; the issue is that the software vendor can not easily provide that it does not.

By stark contrast it is impossible, or at least far more difficult, to perpetuate false rumours about open source software by sheer virtue of the very simple fact that the source code can be freely inspected by any person and the truth is laid plain.