There is a long story behind the names Jubula and GUIdancer but the short version is that, as of 2015, the name GUIdancer was retired. The tool named Jubula contains everything that the previously-named GUIdancer did.
Back in 2004, BREDEX started developing the test tool GUIdancer. It was released in January 2006, and had reached version 4.3 by the end of 2010. At the beginning of 2011, BREDEX changed their business model from licenses to services, and open sourced much of the GUIdancer code in the Jubula Project at the Eclipse Foundation. GUIdancer remained a commercial tool, based on Jubula and offering additional benefits and features. Having "dipped our toe" into the open source world, we were convinced, and made GUIdancer and Jubula functionally equivalent for the standalone versions in 2013. In 2015, we retired the name GUIdancer so that there is now only one name.
The Jubula code is licensed under the Eclipse Public License (EPL). Many Jubula features can be installed into an existing Eclipse installation, or you can download the Eclipse for Testers package, which already contains the Jubula features. The Jubula features hosted at Eclipse (e.g. in Eclipse for Testers) are restricted to code that can be published under the EPL.
The standalone version of Jubula can contain code that is not EPL-conform. The standalone version contains the full feature set.