Wireshark was initially developed by Gerald Combs. Ongoing development and maintenance of Wireshark is handled by the Wireshark core developers, a loose group of individuals who fix bugs and provide new functionality.
There have also been a large number of people who have contributed protocol dissectors and oher improvements to Wireshark, and it is expected that this will continue. You can find a list of the people who have contributed code to Wireshark by checking the About dialog box of Wireshark, or have a look at the http://anonsvn.wireshark.org/wireshark/trunk/AUTHORS page on the Wireshark web site.
The communication between the developers is usually done through the developer mailing list, which can be joined by anyone interested in the development activities. At the time this document was written, more than 500 persons were subscribed to this mailing list!
It is strongly recommended to join the developer mailing list, if you are going to do any Wireshark development. See Section 1.7.5, “Mailing Lists” about the different Wireshark mailing lists available.
Almost any part of Wireshark is implemented in plain ANSI C.
The typical task for a new Wireshark developer is to extend an existing, or write a new dissector for a specific network protocol. As (almost) any dissector is written in plain old ANSI C, a good knowledge about ANSI C will be sufficient for Wireshark development in almost any case.
So unless you are going to change the build process of Wireshark itself, you won't come in touch with any other programming language than ANSI C (such as Perl or Python, which are used only in the Wireshark build process).
Beside the usual tools for developing a program in C (compiler, make, ...), the build process uses some additional helper tools (Perl, Python, Sed, ...), which are needed for the build process when Wireshark is to be build and installed from the released source packages. If Wireshark is installed from a binary package, none of these helper tools are needed on the target system.
Wireshark is an open source software (OSS) project, and is released under the GNU General Public License (GPL). You can freely use Wireshark on any number of computers you like, without worrying about license keys or fees or such. In addition, all source code is freely available under the GPL. Because of that, it is very easy for people to add new protocols to Wireshark, either as plugins, or built into the source, and they often do!
You are welcome to modify Wireshark to suit your own needs, and it would be appreciated if you contribute your improvements back to the Wireshark community.
You gain three benefits by contributing your improvements back to the community:
Other people who find your contributions useful will appreciate them, and you will know that you have helped people in the same way that the developers of Wireshark have helped you and other people.
The developers of Wireshark might improve your changes even more, as there's always room for improvement. Or they may implement some advanced things on top of your code, which can be useful for yourself too.
The maintainers and developers of Wireshark will maintain your code as well, fixing it when API changes or other changes are made, and generally keeping it in tune with what is happening with Wireshark. So if Wireshark is updated (which is done often), you can get a new Wireshark version from the website and your changes will already be included without any effort for you.
The Wireshark source code and binary packages for some platforms are all available on the download page of the Wireshark website: http://www.wireshark.org/download/.