Forum OpenACS Q&A: Response to the dilemma of competition in development of ACS

Of course, the problem of hijacking isn't unique to open source software, either.  Proprietary libraries distributed in binary form can be hijacked just as easily if they have published API's.

And there's the outright piracy problem with proprietary software.  The financial motive to steal proprietary software is certainly much stronger
than the motive to hijack something that's already free.