Free GG is very simple Instant Messenger using popular in Poland Gadu-Gadu network. Application is built with BDS2006/Turbo C++ Explorer and is released under GPL v2 license. Project is based on sources found at http://sadysta.ath.cx/projekty/freegg/.
Since this messenger network is not popular outside Poland, English version of this page is incomplete. There is no translation of FreeGG and if you are not familiar with Polish language I can not recommend it to you. Instead try free and open source Pidgin (both Windows and Linux) or original Gadu-Gadu client. Original client may be also required to create new account as creation of new accounts using older protocol version is currently disabled by provider and/or this function could be not implemented in third-party applications.
If you are not going to contact Gadu-Gadu users on a daily basis, than official www client might be option for you.
If you are still interested in source code or binary please switch to Polish version.