These are resources for developers of QuickFIX/J, not the developers who use the tool.
SourceForge Project Site
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 Issue Tracking
Jira is used for issue/bug tracking and release management. It can be found here.
SVN commit comment
When committing in SVN, the developer must follow this pattern in the comment:
QFJ-nnn: <title of JIRA ticket>