Nothing is free.
First off lets split your question(s) up.
1. Isn't the software free for download?
No, not always.
As Zizouz212 wrote on a similar question:
You can pay for open source software. With Open Source, the source code must be made available, and provide options for forking and the like. Compiled versions can be paid for.
Like many other programs, open source software is generally similar to proprietary software. For developers, they can get their hands on code, and fork and experiment. For consumers, many might not see much of a difference, except that they may see it as open information.
2. How can the usage of Open Source Software cost so much?
Well, now that you know that you CAN indeed pay to use open source software you can imagine compaines / govenments such as Munich, they wold need to pay for:
- Changes to the software
- Bug fixes
Even though they have the source code, they have no one to change / fix it, so they would need to hire experienced developers which would cost money.
Which costs are involved in using Open Source Software/Free Software?
This is a tricky question, mainly because it depends on many things but here are a few just as an example:
- Developers (hiring them)
- Food for developers
- Website hosting
- Power (electricity bill)
These are just a FEW of the costs that could be involved.
Keep in mind that just because something is open source does not mean it is free, people have to pay for dinner somehow!