These are resources for developers of QuickFIX/J, not the developers who use the tool.
Source code is available from the SourceForge Subversion repository. Information on accessing the repository can be found here. You can also browse the Subversion repository.
As the SourceForge Subversion documentation states, you'll generally want to checkout the trunk rather than the root of the repository.
svn co https://quickfixj.svn.sourceforge.net/svnroot/quickfixj/trunk quickfixj
Jira is used for issue/bug tracking and release management. It can be found here.
QFJ uses the Bamboo CI server. Latest build status is here. RSS feeds are also available on the build status page.
When committing in SVN, the developer must follow this pattern in the comment:
QFJ-nnn: <title of JIRA ticket>