[Christopher] Now let's talk about another type of royalty-free product—open-source software.
You've probably heard of open-source and you probably use open-source software everyday without realizing it,
but what actually is open-source?
Open-source is a type of license.
There are actually lots of different licenses that are open-source licenses and we'll learn about some of those in a second,
but something that's open-source means that the product is free and it's code is available to the public,
allowing anyone to tinker with it, learn from it, and create new things based upon it.
Now I said free—I didn't really mean free in price. You can buy and sell open-source software.
Free is really short for freedom. It's an idea.
It's about licensing the creative work in such a way that others are encouraged to use it, adapt it, build on it, extend it.
So a program like Adobe Photoshop or like iTunes—these are not open-source programs,
but there are lots of open-source softwares and frameworks out there.
Android, for example, is open-source. That's one reason it's become such a popular smartphone operating system.
It's free for any phone manufacturer to use on their devices.
Firefox, one of the most popular web browsers, is open-source software.
Most of Google Chrome is—that's my browser of choice—
but some components of it, like the built-in Adobe Flash software, are not open-source,
but its foundations are open-source and anyone can download that code from Google's website.
There are open-source alternatives to many popular programs.
Gimp is a photo and graphics editor similar to Adobe Photoshop, and it's open-source software,
and OpenOffice is an alternative to Microsoft's office suite.
A lot of the stuff we teach here at Treehouse is open-source.
PHP and Ruby are open-source projects.
MySQL, the database management system, is open-source and, of course, WordPress is also open-source software.
Now just because something is open-source doesn't mean that it's not copyrighted.
An open-source license is still a license.
It may be very open and free to use, but there's still that license attached to that copyrighted product,
whatever it might be, and it is your job to abide by it.
As I mentioned before, there are lots of different open-source licenses out there.
Each has that spirit of freedom and openness to it, but many open-source licenses
do add other important terms to the license that it's important to read and understand.
The GNU general public license is the most popular open-source license.
WordPress is licensed via the GPL
It's free to use, modify, and distribute, but one of the terms of the GPL
is that when you create something and license it with a GPL license—
and this is a quote—"You must pass on to the recipients the same freedoms that you receive."
This means that if you take a GPL-licensed piece of software and create something new based on it
it must also be GPL licensed.
All right, in English—let's take a real-world example: WordPress.
Any theme or plug-in you create for WordPress is automatically GPL licensed.
Those are considered derivative works, meaning they were new things
created from the original WordPress software—meant to work with it.
You have to make the source of it open to everyone.
Now I hear what you're saying: "You yourself, Christopher have mentioned premium WordPress themes.
I see people selling them all the time, right?" Well, what they're actually selling there is support.
See, someone can sell you a WordPress theme but, under that GPL license,
there's nothing to stop you from just giving it away for free to somebody else.
Most sites that sell premium WordPress themes are really providing a service.
By purchasing the theme you're also purchasing some type of support package for it.
So if you have questions about it or something goes wrong, they're there to help you,
or they will often promise to provide updates to the theme as WordsPress software updates.
WordPress themes and plug-ins, as derivative works based on the original WordPress software,
are automatically GPL licensed. Remember that the next time you create a new WordPress theme.
The work that you are doing may end up being used by someone else someday,
just like the theme that you built is probably based off the work of yet another person. That's what open-source does.
It encourages that type of sharing and openness, but don't mix up the theme, or the framework,
or the software that you're using with the content that you're creating with it.
Blog posts that you write using WordPress are still copyrighted and don't have to be shared like a WordPress theme does.
Just because you're using OpenOffice to write a book doesn't mean that the book itself isn't copyrighted.
There's a big difference between the software that you use to make something and what you actually make with it.
You can't copyright a hammer, for example, but you can copyright the sculpture that you make using the hammer.
Does that make sense? Take a quick quiz and let's make sure you understand open-source.
Then we're going to talk about something you've probably heard about already—Creative Commons.