Updating mac os 10 5 system requirements
Text Wrangler is freeware and does not require activation with a product serial number.
This version is recommended for all Text Wrangler customers whose Macs meet the specified system requirements.
We regularly release new versions of the Dropbox application with additional features, better performance, and enhanced security, and these versions are not always compatible with older operating systems.
If you received a message from us but believe you are already running a newer version of OS X, you may have your account linked to multiple computers or mobile devices.
I'm not able to check it now, but I remember for sure that the computer was bought around 2009-2010, and it is one of these two (1, 2), which should mean that it can be upgraded even up to Maverick. You can use System Profiler to find to Model ID of your friend's i Mac (see this KB article) -- that'll tell you for sure which generation of i Mac you have, and whether it can run Mavericks (i Mac7,1 and later). From there, all upgrades come electronically from Apple.
Again, if the hardware is compatible, you can jump to Mavericks to free (though unlikely for most 10.5 era hardware).
Sometimes these can indicate hardware problems, but otherwise may suggest software configuration errors that may migrate with the system during the upgrade.
You may be signed out of your account on the desktop client as early as May 18th, 2015, and will not be able to sign in again until you update to OS X Snow Leopard 10.6 or later.