get paid for contributing in open source projects

Hi guys,

I started recently to have real enthusiasm to contribute & work on open source projects .
there are many popular and successful java open source projects like :
-Apache
-Eclipse
-NetBeans
-Lucene..and many of such famous java open source project.

my questions for people with previous experience in OS projects:
-is contributing in these projects only a volunteer work ?
-is it possible at all to get paid for your valuable contribution in some of these open projects ?
-In General ,how can someone make profit while writing open source projects?

I'm a supporter of freedom and sharing; but still i need to earn my life and don't want to die from hunger :-)

thanks

It depnds on the project. Have a look at this link

http://www.indicthreads.com/blogs/251/open_source_employee_volunteer.html

Most open source contributors are volunteers.

Some companies pay some employees to work nearly exclusively on open source projects.

Some companies ask employees to do volunteer work as part of their work week, and open source is one way to do that.

Contribution to open source projects can provide community recognition which can help with a career.

Eric S. Raymond's writings (http://www.catb.org/esr/writings/cathedral-bazaar/) cover open source economic models (see The Magic Cauldron).

--Mark

thanks for the replies so far
I Indeed started to read the magic cauldron before posting this question. this book has many answers to this issue...

thanks all.