The reasons for the debate about open/closed source options vary from ethical issues to practical issues.
Possibly the biggest advantage of open source software is the fact that everybody has the right to modify and tweak the source code. This means the code can be implemented in other pieces of software and adapted to changing environments.
This access to the source code means that suddenly any number of people, skilled or otherwise, have now become programmers of the open source code. The implications of this are that bugs can be easily fixed. With closed source if there is a bug in certain software the user must wait for a new release whereas in open source the code can be altered and the bug can be fixed.
The re-distribution of open source code is also promoted. Meaning that a bug fix can be instantly re-distributed instead of having to wait for a newer release. This also leads on to the point that a large software company who is providing closed source software may prolong bringing out a newer version of some software in order to maximize profits. As open source software is usually free, and there is no profit to be made, new versions are being released all the time.
Another advantage of open source is that so many people have access to the code. This means that there are a large number of sources for support. Trying to find support for an "out of the box" piece of software means contacting the software company looking for support, however open source developers are everywhere and theoretically any number of them could offer support.
There is also another big advantage of open source software and that is that it is usually completely free in every sense of the word. It is free to use, free to distribute, and free to modify. To the general public this means that they do not have to pay anything for the product where as a closed source alternative could set them back hundreds of pounds.
Just as development is free and encouraged in open source, it is also not compulsory. Closed source software companies pay salaries to people to develop the software and therefore development is pretty much guaranteed.
Quite a large disadvantage to open source software is that as so many developments are going on at the same time it is hard to keep track of which version is the most up to date. This is also due to the fact that advertising is not as prominent in the open source industry, mainly because most developers are non-profit making. This lack of advertising and frequency of developments can sometimes cause confusion of which product is the most up to date.
There is an issue where the line between open and closed source blurs. Many open source projects are developed from many different peoples codes and this can make it a struggle to effectively sort out who's is who's. It also increases the risk that a bit of closed source code might find itself in there and therefore render the project illegal. However. the open source licensing is geared up to help the contributor.
Many businesses opt for a closed source alternative when it comes to their server. Some of their issues are outlined at the Microsoft Compare website. This presentation however is from a closed source software company and they may be slightly favourable to their product. They claim that Microsoft offer increased reliability, security, choice, manageability and interoperability. They back this up with case study examples of government organizations that use their Microsoft server 2003 product.