Yowsup https://github.com/tgalal/yowsup MIT License
It is a library that implements WhatsApp's protocol. It is built on community effort of reverse engineering WhatsApp's protocol. I created this in first place to bring WhatsApp on an unsupported platform (Nokia N9/ meego platform)
Wazapp https://github.com/tgalal/wazapp GPLv2 License
This is a UI frontend to Yowsup for Nokia N9. Nokia N9 is the only smartphone produced by Nokia which never got WhatsApp support. I created this client because I wanted to use WhatsApp on my Nokia N9. The code is totally decoupled from Yowsup, and does not use WhatsApp in its name. You can see its icon here http://everythingn9.com/wp-content/uploads/2012/05/wazapp.pn... which for me looks different enough from official client's icon.
OpenWA https://github.com/tgalal/OpenWhatsappBB10 GPLv3 License
This is also a frontend to Yowsup, but for Blackberry 10. It is a little bit similar case as Wazapp. I created this for BB10 when WhatsApp initially said they're not supporting that platform. Again, this is decoupled from Yowsup, has same icon as Wazapp. Its name though on Github is OpenWhatsappB10, as a project name. However, the real app name is OpenWA. Perhaps a rename of the repository would be sufficient ?