Answer 1

There are different motivation behind it:
1) They want to genuinely help. And sharing is caring. ;)
2) They want to make a difference and solve a problem
3) They want to learn how to program. The standards in Open Source Projects is pretty high. So if you make it there, you can (basically) make it everywhere
4) It's their way of promoting their skills to get a (better) job and/or build up their portfolio. Some employers will look through or developers will recommend you to their employers.

Answer 2

Good Question 🐈
Most of the people copy from their!
But they have no other option. If they wanna share the code they have to make it public...otherwise no one will get to see your code ;)

Maybe I'm wrong :/

Answer 3

Employment aspect: Silicon Valley companies ask you for your github. And yes--so does github--if you apply there.

Answer 4

I disagree with Dayve. People who create open source code aren't afraid of people copying their code or simply put up with it because it's the only option.

The open source mentality is all about sharing, not ownership. A lot of great code, including some of the most popular applications and tools, are built upon the foundation that open source allows. It's a community, first and foremost, of like-minded people.

Employers these days respect people who share their projects on GitHub and similar sites, sometimes it is even expected to have a portfolio online. Hogging your code is mostly a thing of the past and a lot of successful companies have shown that you can be open source and thrive despite of it - actually, often BECAUSE of it.

Answer 5

also, not every code is marketable. if your not going to make money from it, why not share it?

Answer 6

Guess where you can find the answer to your question?
On Github!
this is the Rufus FAQ, have a look at the developer reasons:
https://github.com/pbatard/rufus/wiki/FAQ