If you're trying get the data off a disk, do not mount for read/write access or you will almost certainly loose your data.
Follow these instructions on how to mount an HFS+ disk on Linux. But please mount it read-only. The tricky bit is finding the start of the partition, but that's covered. http://www.64lines.com/mounting-hfs-plus
OK, I found the ubuntu disk utility. I've begun the copy (it's going to take forever with USB 2.0, not to mention the source disk is sick), but once it's done, I'll mount the new disk and try Migration Assistant on the Mac.
Thanks for the help, guys. I've played with this off and on for the last day or so, and it appears that when a drive is formatted on a Mac with the journaling option, it mounts on ubuntu as read-only. When I disabled journaling in my format, I could then write to the drive.
Not 100% sure about this, nor do I know if it applies to all flavors of Linux.
Anyway, I think I've beaten this to death as far as this forum is concerned. Thanks again...