Forum OpenACS Q&A: Response to GNU Public License and Mozilla Public License

Al, another issue you should be aware of is that the MPL and the
GPL are incompatible, which means that OpenACS can't share
code or (perhaps more importantly) data models with ACS Java
anymore. By switching licenses, ArsDigita has definitively forked
the code bases. OpenACS can no longer even *try* to develop in
parallel to ACS Java, because to do so would be to risk violating
the license.