This week, the Greens have joined together with Friends of the Earth, New Internationalist, People and Planet and the Free Software Foundation to call on other social and activist groups to reject Microsoft's Vista operating system and encourage the use of free software.

Free and open source software (FOSS) is written by teams of developers from different companies and organisations, and can be used and shared by anybody. The 'source code', which make the program work, is made available to all users to copy and rewrite, unlike conventional software, where only the copyright holders can make changes or legally distribute copies – usually for amounts of money that bear no relation to the cost of making and distributing a disc.

The main benefits of FOSS to a small organisation are, of course, cost and independence. Most of the software is free, and often it is very easy to use. It almost always works well with other programs and doesn't try to make you buy a whole package of related products.

With free software and some second-hand or refurbished hardware, an NGO or small business can start up an office with a couple of hundred pounds, rather than spending tens of thousands on new hardware and the vast range of software licences you need in order to do the most basic office tasks. Microsoft or Mac operating systems, along with Microsoft Office and Acrobat Professional for making pdfs, don't come cheap, even with non-profit discounts.

Professional support for non-profit free software is growing fast, with groups such Tactical Tech and Women's Net producing a collection of peer-reviewed software tools that do everything an organisation needs to get itself going, all bundled up as 'NGO In a Box'. Other tools such as the free 'relationship management' tool CiviCRM (which will keep track of your members, volunteers and donors all in one place) are helping NGOs to free themselves from the tyranny of the, frankly awful to use, Microsoft Access.

“This all sounds lovely,” I can hear you thinking. “But why is the Green Party getting involved? Surely this doesn't have a lot to do with the environment?”

Well, it does and it doesn't. Specifically on Vista, when it launched this year we alerted the world to the wasteful attitude to hardware Microsoft's new operating system was foisting on its customers. The demands of the new system meant that many components in the computers of early adopters would be unable to cope, so potentially millions of perfectly good sound and video cards could be dumped in the bin as a result of the switch. We went so far as to call it a 'landfill nightmare' and I said that “future archaeologists would be able to identify a 'Vista upgrade layer' in our landfill sites." OK that was an exaggeration, although not much of one.

But apart from the environmental benefits of free software in avoiding the throwaway festival that comes with a Microsoft upgrade, there are philosophical reasons for the Green Party's affinity with free and open source.

Greens are often thought of as being against globalisation in all its forms. However, globalisation of shared information is a good thing, especially if it means small and local economies can share the benefits of collaboration and become independent of multinational corporations. If you think this sounds idealistic, take a look at Brazil, where they are saving vast sums of money by using Linux to bring computing to the favelas, or the One Laptop Per Child project, which is using open source software to drive a very cheap and simple computer that will be distributed to children throughout the developing world.

We first adopted policies in favour of FOSS in 2005 and have been gradually moving our office systems to open source solutions since. We now use Linux for our web server and website and a range of open source programs in the office. Along with signing up to the Free Software Foundation's call for more NGOs to take advantage of the benefits, we're extending this call to government too.

Think about it. The problem of designing a computer system to run a library or make hospital appointments is roughly the same everywhere in the world. With every government hiring IT companies to create separate, proprietary systems, a lot of private profit is created. However, the governments will not own the source code at the end of the process and the companies can charge the same to each government they sell their software to. It's the same kind of deal as Microsoft charging hundreds of pounds for an MS Office licence and making astronomical profits, because the cost to them each time the software is installed is – literally – nothing.

Under an open source model, governments instead collaborate with each other and pay IT companies to develop open source systems. This means the problem can be solved once and then implemented everywhere without charging taxpayers again and again for the same thing. Upgrades and further developments can be funded and carried out collaboratively too, and this can lead to enormous savings overall. Health sector projects are already underway, such as the Open Health Information Project led by Oregon State University. Getting the UK government to embrace this new approach could bring huge benefits to this country, given the billions being put into public sector IT at the moment.

Using more FOSS in government could do more than save money and development time, it could also free us from having to get involved with companies like Lockheed Martin, who are now in the final round of selection to run the 2011 Census (as I have blogged about before).

The Census Alert campaign would be completely unnecessary if the government was able to take and adapt a free, open-source census-gathering system, developed collaboratively and openly with other governments, with data security and privacy in mind. Instead, unless the campaign succeeds (which it might – we now have Campaign Against the Arms Trade and several MPs supporting the campaign) it is likely we will have to put up with the black-box, proprietary software provided by Lockheed, plus their assurances our personal details will be safe. I know which model I would rather trust.