Brain-Extension is a project mainly written in Scala, it's free.
TODO
Use the NETLOGO environment variable to tell the Makefile which NetLogo.jar to compile against. For example:
NETLOGO=/Applications/NetLogo\\\ 5.0 makeIf compilation succeeds, sample-scala.jar will be created.
The NetLogo brain extension is in the public domain. To the extent possible under law, Uri Wilensky has waived all copyright and related or neighboring rights.