The name stands for "GeneralPurpose Abstraction Layer". GPAL is a set of C++ classes which are used to represent any kind of data and to manipulate them. Thanks to SWIG, it is usable in many programming languages.
JRET (Java Reverse-Engineering Tool) is a program that is capable of reconstructing sequence diagrams from JUnit testsuites through dynamic analysis. It is written in Java/AspectJ and provides a GUI as well as command-line possibilities.