Most people I've met, when I talk about Open Source Software, have a hard time understanding why people would choose to give their software away for free. One of the questions I hear often is, "But then how do you make money?"
Actually, you have it all wrong. Very few applications written by developers today are ever sold. Most applications are "in house" - in other words, they are written internally by a business to fulfill the needs of the business, as opposed to being written to be sold.
What this means is that most developers working on open source software have a normal day job, writing software to fulfill a business' needs. And therefore most open source developers spend their own free time writing open source software.
But if not all OSS developers are writing in-house code, then how do these developers only writing OSS make money?
Some developers are employed by a company to write OSS. The most well known example of this is Linus Torvalds, the original author of Linux. He, and a number of other kernel developers, are employed by a foundation which is funded by the likes of Intel, AMD, Nokia, IBM and other big name companies, who each have an interest in the development of the kernel.
Some businesses provide a service around OSS. For example, Red Hat provides server and enterprise desktop services. They sell software+support packages to companies, which pay for the installation, configuration, telephonic and/or on-site support, and subsequent software upgrades for the duration of their support contract. Red Hat employs developers to achieve this goal.
Some folks sell open source software. This is rare due to the fact that the open source community in general believes not only in free-as-in-freedom but also free-as-in-beer, but it happens none-the-less. The most "restrictive" of all the OSS licenses, the GNU General Public License, does not prevent you from selling your software, it just guarantees that you distribute your source code with your software, and you do not restrict your customers from distributing your software in any way they want. My friends across at the 8bit Network do this. They have 4 very stunning Wordpress themes that they sell, but are licensed under the GNU GPL.
Another way I have seen to make money off OSS is to write web-based software, and then offer a hosted version of the software for a monthly fee. Indifex, the company that writes Transifex, does this. Transifex is a web-based open source translation manager, and Indifex has a hosted version of Transifex, where you can sign up to use their software to manage the translations of your project(s).
Businesses can also offer their software under dual licenses. Trolltech (as they were known before Nokia bought them) used to license the Qt GUI toolkit under both the GNU GPL and a commercial license. This meant that companies that wanted to use Qt to write proprietary software could purchase a license to do so.
Some businesses use a variation of the above, where they have a "community" version of the software which is open source, and an "enterprise" version which contains proprietary extensions that big businesses would find useful. KnowledgeTree does this, with its open source community edition, and its proprietary enterprise edition.
Some developers also offer to implement certain features for a price, so that companies who would like a certain feature implemented sooner can pay the developer to work fulltime on that feature.
Lastly, some developers write proprietary extensions for their open source projects. This allows them to give the core system away for free, while making money off value-added extensions that enterprises and the like would be interested in.
I'm sure there are other ways to make money using open source software, but these are the various models I have seen in the real world.
At this stage people are likely wondering how this relates to churches.
Quite honestly, supposedly Christian software companies are the worst when it comes to using and/or producing open source software. Every latest church management system and church website system is written in Microsoft's .NET technology, relying on proprietary extensions which only run on Windows Server. And it is not just the proprietary applications, the open source systems are also written in .NET and have to run on a Windows server.
Open Source Software is all about freedom... including, I would think, the freedom to run it on the platform of your choice. Forcing me to run Windows is not giving me the freedom to choose my platform.
When I took over the OpenLP project, that was my goal and aim, to transform this Windows-only program into a truly "free" application. Now we have an open source worship presentation application that runs on more platforms than any other worship software out there. The net effect? You can run in on your platform of choice... Even Windows ;-)
So what's my point in all of this? My point is that you *can* make money off open source software, and it doesn't have to be restricted to Windows. You can write software for the church, as many Christian developers I'm sure wish they could do, make it open source, and still put bread on your table.