Well, there are a lot of *swift* packages in Debian, but they're mostly related to the Openstack thing, and Swift IM was there before Apple came with their "Swift" language, so it was not that used at the time of Swift IM's creation =)

And Swift IM _is_ in Debian and has been for a long time (included in Wheezy), it's just not in Debian 9. AFAIK the Debian package is maintained directly by upstream, maybe part of the process could be improved somehow...