Open Source means that the source code for the software built is completely open and is available to the public for free. Open Source software need not be built on open source languages like there are many open source projects built on technologies from microsoft like .net etc.
I understand your interest in open source is because you might have heard about GSOC from some people in your college and you might have also heard it is an internship that pays very well (5000$ actually for 3 months).
Facts :
1. GSOC was started by Google which had one motive in mind and that was to educate people about open source technologies and get more free code in the market.
2. It is not an internship.
Now that you know what GSOC is, lets talk about open source development.
Open source development wont be much helpful in getting a job although there are some companies that see this as a criteria but many companies only care about your GPA and mugged up algorithms.So be advised, open source developers develop software because they want to not because they have any ulterior motive in it like money.
For leaning and getting into open source development i suggest you get acquainted with some open source platforms like linux or BSD (my suggestion start with Ubuntu/Linux Mint), as windows in itself is closed source and once you get into open source development you would want to play with as much source as you can. secondly these operating systems are really good for daily use and coding.
Languages like C/C++/Java/Python/RubyRails/HTML5/JS are the most used languages in open source development. there are many other languages used but these will be the most common. As you are efficient in 3 of these you must now get to know your interest. I suggest you go to github.com and checkout the open projects according to your interest and knowledge base. I would have some software i like and use a lot and started fixing bugs i found in the software and sending patches. You should start hanging out at IRC because most of the open source communities talk at IRC.
I am also a student in an Indian College. I also had the same questions when starting out. You are free to contact me for any more help.