For a last supported iTunes application to work in your Leopard 10.5.8,
you'd need to get iTunes version 10.6.3. ~ With that you can still see
music for sale, use the application to transfer music from CD to your
iPod or in-Mac libraries. And use dozens of free 'internet radio' stations.
The iTunes application was not a software update download channel
as present iTunes Store, Mac App Store, or iBooks Stores are now.
For Tiger 10.4.11 the last supported iTunes version 9.2.1 works, and can
be found after some looking, in the archives of Apple Support download.
This link (blue text) is supplied; but probably won't work in Leopard 10.5.
Word processors? You have a native Mac OS X version in TextEdit. That
also can do more than just text; not nearly as good as some. You may be
able to get light-weight text editors such as 'Bean' and perhaps find an
archive of older titles... Maybe without adware, or doctored junk files with
only the name of the desired application in common with original content.
Bean for Mac older versions 2.4.5 + 3.1.1 are here (PPC Tiger + Leopard)
http://www.bean-osx.com/Bean.html - a word processor for OS X
[Download Bean for PowerPC Macs]
This older version (3.1.1) compatible with PowerPC processor Macs running OS X Leopard 10.5+
[Download Bean for Tiger]
This older version (2.4.5) is compatible with OS X Tiger 10.4+
An old version of AppleWorks 6.2(.9) may be found on orphan install DVD
media; some Macs shipped with AW. I've the last version in my PPC Macs.
(CharlesSoft 'Pacifist' is useful to extract items from obsolete install discs.)
A few existing brands formerly available have been superseded by newest
version builds that cannot work in the old vintage or obsoleted Mac OS X.
Perhaps someone who has time to check or already uses vintage text or
word processing software in Leopard 10.5.8 (PPC) may offer other ideas.
Good luck & happy trails! 🙂