First of all, I'd like to say that the concept of open system can be found not only in computing world, but in almost every field of activity.
What is an open system? Generally, an open system is an complex system built on many components, which interacts one with others through some communication protocols. The function that the system implements must have all the parameters - if any - tunable, and the system must be capable to communicate with other systems. Also, the specifications of the system and the corresponding communication protocols must be described in a freely available documentation.
The standardization have an essential role in the open system's existance: it allows to work in it's interior, which means that the different components could conlucrate, and to communicate with the exterior in a well defined manner. So, the open systems implies the existance of some standards, but the presence of a standard does not necessarly implies the fact that we are dealing with an open system.
The history of computing world shown us that the big companies' tendence was and still is to monopolize the market and to impose proprietary systems and architectures. But we all know that - at least in computing world, the monopol is inconceivable.
The manufacturers have also the tendence to use the "open" and "open system" terms for the products they promote.
In many cases, the standardization it's nothing but a deceive imposed by the big companies trying to impose a monopol. There are, of course, some exceptions. A positive example is the NFS (Network File System) standard, created and supported by SUN Microsystems.
We should try to compare the "standards" created by Microsoft - for example (as MFC or DDE) -, with an open standard, such as one in the RFC series (which means "Request For Comments") - let's say ftp or telnet. The big difference between these ones is that the first one is imposed, and the second one is proposed.
The "free software" (which means freely distributable software) phenomena is a reality. As a proof is the growing popularity of the Linux operating system. The Linux building project is one of the biggest ones that has been done in the history. It was done by hundreds of programmers all over the world, and have now couple millions of users. The role the Internet had in this project development is obvious. From an global point of view, the Internet is nothing but a huge open system.
I think the The Free Software Foundation and the "free software" movement in generally will have an important contribution to the evolution and imposal of open systems. The standards created in free software world are not controlled by any organisation, but generally speaking this world is producing much more open systems than the companies that creates proprietary software - mainly because it answers much quicker at the users' demands.
Following the open system model, the systems can be built on many small components, instead of building monolithts, which are difficult to change and with minimal extension capabilities. The different components can be provided by different manufacturers. But this require interoperability between components, and the interoperability leads to interdependence. We saw that the big companies' tendence is to create proprietary systems. Will this companies agree to follow some standards, instead of imposing their own ones?
The interoperability is definitely the key of open systems. Every complex system require the ability of component objects to operate as a whole system. The components must conlucrate and efficiently communicate one with others.
We are confident that the movement from monolithic systems ("black boxes") towards open systems will accelerate in the future.