"Open Source" means different things to different people and not everyone accepts the OSI definition, there are even people who are angry at ESR for grabbing the phrase for himself and making his definition the most popular one.
http://jordi.inversethought.com/blog/5-things-we-have-forgot...
And those people are wrong. The OSI definition is the definition. Those that want it to mean something else are trying to fool people, which we call "open washing."
Much like many countries have a mile, if you started using Roman miles in England or the USA people would think you misleading
To expand on what you said: the term open source has a specific meaning and it doesn't mean "the source is available". From Wikipedia:
> "Open-source software (OSS) is computer software with its source code made available with a license in which the copyright holder provides the rights to study, change, and distribute the software to anyone and for any purpose."
Once upon a time most of the JDK had the source available - with all rights reserved. It was emphatically not OSS.
That is not what "Open Source" means.
> but legally, the copyright is still owned by the authors
In Open Source/Free Software, the copyright on the software is still owned by the original authors.