At Cohesion we work within a CMS system that we've built in-house, over time, tweaking and modernising as required by technological advances and the needs of our clients change. Over the time that our CMS has been in development, and usually during the discovery phase with our clients, we are sometimes asked whether we develop in open source, and the pro and cons of open source development.
An open-source CMS is one where the code behind it is shared openly within a global community. As such a large number of developers contribute to the development resulting in a library of code that can be used to good effect for a range of solutions. There are many arguments toward open-source and like any good idea, there's a place for it within the web development industry.
When we made the decision against open source however, we considered the benefits did not outweigh the risks and downsides to open-source, and that our clients came to us because they were interested in having the best solution for their business requirements - not simply to have their website fit into whatever enables the developer to make the most money from it.
Open-source software is just that - 'open'. Because it's also free (which doesn't mean free to the client as any developer still has to spend time to implement), and because the community is globally large, the number of people or hackers who are trying to breach the software is also large. Custom deployments make little sense to attempt to hack as the time it takes to break into a site cannot be applied on a broader scale.
Closely linked to security, custom website builds provide a greater level of privacy toward your business methods, unique selling points, and of course considerations around the privacy and security of your data and that of customers, members or trade members all of whom may have data - critical or otherwise - stored on your website. A higher degree of security also means a greater level of privacy is afforded to the data integrity of your business.
Yes, open-source has a good community of developers behind it, but the fact that it isn't "owned' by anyone can also be its biggest distraction and drawback - there is ultimately no accountability to customer service. The buck really doesn't have anywhere to stop. Lack of basic technical support is one thing; get hit by a virus or hacked, and you're looking at a wholly different set of problems.
Building a site from a pre-existing open-source library does not necessarily equate to cost savings. The time to implement and customise within a framework built by another developer can be extensive, regardless of whether that library was built by one or hundreds of collaborative developers. Frequently the cost of implementing a plug-in can be lengthier, and therefore more expensive, than developing from scratch - especially where the plug-in needs to work to achieve objectives for the website but at the same time meet the requirements of the CMS which has been collaboratively constructed.
CMS systems which are developed with the intention of being used by the masses must accommodate resources for hundreds of possible outcomes, the majority of which will not apply to your site. As a website loads, an open-source system can call anywhere between 20 - 200 or more resources, where our standard is seldom ever over 20. We practise totally lean code because the less resources your site needs, the quicker it loads, the higher the 'pagespeed' rank by Google. And importantly, the leaner the code, the fewer issues there are between browsers and platforms.
Bottom line - If we believe you'll benefit from an open source platform, we'll let you know and we'll recommend it. Likewise if you insist on it, we'll demure to your wishes. We'll always do what we believe is right for your project, your budget and your future requirements.