http://www.infosun.fim.uni-passau.de/Graphlet/
HJG 2014-04 - "Graphlet (no more available)"
Judging from the information on the site above
The source code for Graphlet has been released under the Gnu Public License.
Graphlet is a toolkit for implementing graph editors and graph drawing algorithms. Graphlet runs on UNIX and Windows systems, and uses the same source code on all platforms. The key to this level of portability is that all platform dependend features have been deferred to Tcl/Tk. Graphlets design makes it easy to port the editor to any other platforms, provided that the LEDA and Tcl/Tk toolkits are available.
Graphlet comes with a large set of already available algorithms, including: