YAWL is a very powerful state-of-the art BPM environment, which is open source, and aims to be easy to use and to install. The latest academic insights are continuously integrated into the environment which makes it uniquely positioned.

Yes, both the YAWL workflow system and process editor are released under the LGPL licence.

For more information on the benefits of open source software, please see the Open Source Initiative pages.

To a large extent YAWL was inspired by Petri-Nets, however a common misconception is that YAWL is simply a set of "macro like" extensions for Coloured Petri-Nets.

YAWL extends Petri nets with concepts for multiple instances (where at runtime a task may have multiple instances active at the same time), the generalised OR-join (where a construct only waits for further triggers if these can indeed arrive) and cancellation (where a collection of activities can be terminated through the execution of a certain task). Descriptions of these patterns can be found on the workflow control flow patterns site. Technical details on these extensions can be found in the original YAWL Paper.

Firstly, YAWL provides stronger support for the workflow patterns (e.g. see here). Of particular note are YAWL’s support for the control-flow perspective and the resource perspective. Generally speaking the stronger patterns support means that it is easier to specify complex workflows.

Secondly, YAWL has a formal semantics. This means that it is not necessary to debate the precise meaning of certain constructs and that there shouldn’t be a discrepancy between a model and its implementation due to interpretation differences. As a result of having a formal semantics, YAWL can offer powerful means for design time workflow checks (see for example the paper business process verification - finally a reality!)

Thirdly, YAWL offers comprehensive support for dynamic workflow, where workflows need to change after their deployment and for handling unexpected exceptions. In many realistic scenarios processes evolve and not all exceptions are foreseen. Through the Worklet service, dynamic flexibility and exception handling support change, even while a process instance is executing. This means that YAWL can offer superior flexibility support (see also this paper).

Compared to BPMN it is striking that YAWL can handle more control-flow patterns yet is considerably simpler in terms of the number of available contructs (and their meaning). Also, in contrast to UML and EPCs, YAWL models are executable 

We have produced research papers about YAWL and we have written some papers on Control-flow Patterns, Data Patterns and Resource Patterns.

YAWL has been the subject of many news articles. Here is a selection:
 - YAWL simplifies business process management QUT News, February 12, 2018.
 - YAWL: Workflows mit geringem Aufwand erstellen iX Magazine, 1/2017 (in German).
 - IT solution to improve hospital workflow and schedules QUT News, August 03, 2011.
 - That’s QUT for YAWL in SL The Metaverse Journal, October 24, 2008.
 - Lights, camera and action simplified by QUT QUT News, August 01, 2008.
 - Qld uni YAWLs in open source BPM ComputerWorld, July 06, 2006.