OWASP is a not-for-profit entity, that ensures the project's long-term success. Similar to many open-source software projects, we are volunteers from around the world, open to anyone interested in learning more about software security. OWASP produces many types of materials in a collaborative, open way (check some of them out here: OWASP Zed Attack Proxy Project (ZAP) and here: OWASP Test Project)
Our talks can be on any aspect of application security, some of our past talks are: Implementation of Security in the Software Development Lifecycle, Creating secure code requires more than just good intentions, Top Ten Web Defences, and Introduction to Buffer Overflows.
To be a speaker at any OWASP chapter in the world or just at Melbourne Chapter, simply contact the local chapter leader with details.