Ok, I found this:
http://lists.debian.org/debian-mentors/2011/10/msg00195.html
Which points to :
http://mentors.debian.net/package/flex-sdk-4.5
However this leads to an error.
Digging further I found:
http://lists.debian.org/debian-mentors/2011/10/msg00421.html
Which leads to:
http://alioth.debian.org/scm/?group_id=100677
I cannot retrieve from git it fails with:
$ git clone git+ssh://malat@git.debian.org/git/pkg-flex-sdk/pkg-flex-sdk.git
Cloning into 'pkg-flex-sdk'...
fatal: '/git/pkg-flex-sdk/pkg-flex-sdk.git' does not appear to be a
git repository
fatal: The remote end hung up unexpectedly