Is JavaFX open source?
Update Sep 202
For further info see the closely related StackOverflow question:
- JavaFX and OpenJDK
I'd close this question of a duplicate of the above one, but it has already been closed as off-topic and cannot be closed as a duplicate by me. Regardless, the linked question hasn't been closed as off-topic as of now and provides more answers with more detail, so it is a better place to look if you need more information,
Update Dec 2019
For current information on Open Source JavaFX, visit https://openjfx.io.
The current open source code repository for JavaFX is at https://github.com/openjdk/jfx.
At the source location linked you can find license files for open JavaFX (currently this license matches the license for open JDK).
As of February 2013, JavaFX is partially open source and should become almost fully open source over the next few months. The source is hosted as part of the open-jfx project that you linked in your question.
The manifest of the tip of the JavaFX development branch for Java 8 is: http://hg.openjdk.java.net/openjfx/8/master/rt/file/tip
The same page has a zip link, which allows you to easily download the available JavaFX source as a zip file.
The JavaFX source code is not included in the jdk src.zip file currently, but should be eventually before Java 8 is released.
A February 2013 update for JavaFX OpenSource status has been published by the JavaFX development lead.