Stipends are offered to students who are allocated projects.
Google Summer of Code is a global program that offers student developers stipends to write code for various open source software projects. Since its inception in 2005, the program has brought together nearly 2500 successful student participants and 2500 mentors from 98 countries worldwide, all for the love of code. Through this program, the student applicants who are accepted are paired with a mentor or mentors from the participating projects. This enables the students to gain exposure to real-world software development scenarios and provides them with an opportunity for employment in areas related to their academic pursuits. In turn, the participating projects are able to more easily identify and bring in new developers. Best of all, more source code is created and released for the use and benefit of all.
More @ Google Open Source Blog : http://google-opensource.blogspot.com/search/label/gsoc