Source code is the human-readable instructions for a computer, it's what software is made from. Most of the time, having just an program doesn't let you do anything but run it. But, if you have the source code for a program you could read it, learn from it, and modify it to suit your needs.
A license is what keeps software legally free and open. When you download software, you don't really own the program, even though it's on your computer. Instead, whoever wrote the program gives you permission to run it. Before you install most software, you have to agree to a long-winded legal document. That's the license.
Free software comes with a free license, and open source software comes with a slightly different license. Software that's free of charge (freeware) may still be proprietary software if it carries a restrictive license.
More people can work on an open source project, and so over time it's likely to be able to do more and be more secure than software created by a single programmer or organization. But don't take our word for it -- see what organizations and people such as the Free Software Foundation, author David A. Wheeler, and Sean Cohen have to say on the subject.
FOSS is legal for just about any use, as long as you don't try to take source code you didn't write and sell it as your own software. For a longer answer, full of legal details, see an article by Mark Webbink on Groklaw.
Not at all, but since you're getting something useful without paying for it, you may feel like giving something back. You can often do that by donating the developers, but you can also help out by reporting any bugs you encounter, or if you're a programmer yourself, offering to fix a bug. Or you might help tell others how to use a part of the software or do something tricky with it if the manual doesn't already tell you how. Even participating in the online forums to help new users with their problems is a way of giving back.
No, with FOSS you never have to pay to unlock advanced features, or to keep running the software longer than some trial period.
Some people who write FOSS programs do sell other versions that are licensed more restrictively, and for which you might pay something to get more features, but they are separate applications and are covered by different licenses.
It's always wise to worry about malware, which is the catch-all term for software that does bad things to your computer. However, the developers who write FOSS tend to be driven by ethical considerations more than the average programmer, so you're far less likely to find annoying features like these in FOSS programs. But because the code is open, If there were something objectionable in a FOSS program, someone could just take it out and distribute their version.
For many reasons. By writing good code, programmers get known, receive approval from their peers, and may be asked to work on interesting projects. Many feel good knowing their work helps people, and making their code free and open lets them help the widest number of people. Some people have jobs where they work on open source projects, because their company has a vested interest in technology. Others may have started a project as a hobby and it evolved into a good piece of software
Most software is developed by multiple programmers who combine their efforts as part of a project. Most projects have their own Web sites. That's the first place to look for support, in the form of frequently asked questions (FAQ) or technical documents. Many projects also host online support forums, which are like bulletin boards where you can ask questions and get answers from other users or project members.
If you can't find an answer from the project site, your next best bet is to use an Internet search engine, such as Google, and enter the key terms that describe your problem. Chances are you're not the first person who has needed help with your issue, and someone may already have helped out someone else. You can benefit from their experience. In general, there are more online support options for FOSS than you can find from proprietary software vendors.
Most projects have pages on which you can report bugs, or have an email address you can send comments too. Often, the programmers will then fix the problems and release the fixed program. Always search for the problem on the internet first, there is a good chance you're not the first person to experience it
When you report a bug, the programmers need to be able to try what you are doing to see if they can get the bug to happen themselves. So if you want to report bugs effectively, here are a few tips: