jBPM is composed of quite a few different components, not all of which are being developed as part of the jBPM project. Therefore, a number of different licenses apply, depending on which component you're using.
The project is using the Apache Software License (ASL), version 2.0.
Previous versions of jBPM (up to jBPM 4.x) were using LGPL license.
jBPM Eclipse Designer
The Eclipse plugins are developed under the Eclipse Public License (EPL)
The web-based modeler is distributed under the MIT license.