http://macintoshgarden.org/apps/soundedit-16
is this the sound edit icon in your screen grab?

Yes it is.
I've used it from the beginning of times...
Now a days is just a basic destructive audio editor. It support 96Khz but no 24/32 bits audio. No ASIO, no VST, no much... LOL

also,
soundJam
a music player?
http://en.wikipedia.org/wiki/SoundJam_MP
http://web.archive.org/web/20010531202246/http://www.casadyg.com/

My favorite MP3 Player ever!. More powerful than newest versions (Itunes)

this is what became itunes?

Yes it is.

Furthermore, its interface was incorpored into QuickTime at first and in Mac Os X later!
And Apple Numbers app came from the acquisition of Casady & Greene too.

v2.5.3 is the last version?

Yes it is.