On linux, all you need to do is to release tarballs with the source code. Each distribution have its own way to manage its packages. It is 3 main ways to do that, 1) the sources based distribution like gentoo, 2) and 3) the executables way with rpm based distributions like red hat or suze, and the deb based distributions like debian or ubuntu.
Even if you release binary packages, they will or not work on an user computer. This is why all the distribution want the source code. It is a plus for them because this is the only way they have to insure the system consistency. It is a plus for you because they will not only test your software, but also your build system, and they will send you some feedback when they feel it is needed (even eventually some patches).
It is a big problem with iannix: it want everything at the same place. Linux is not windows, and a binary will definitely not be installed in the same directory than a pixmap or a library. See my other post on that matter here.
In the short term, you have to fix the build system. It is not much to do, just the install phase is missing. Well, it can be necessary to make a wrapper script or some changes to the program in order to get it to work with the standard linux files hierarchy. If you do that, it will be as easier for the developers of the distributions to take a snapshot of the git code than for you to release a tarball.
My ebuild for innax is working fine, and it will be very easy for me to test your changes into your build system. I thing than when it will work fine with portage, it will work fine with every package management systems around.