Need help recovering data files from system drive

Hello!

I don't have a lot of system-level experience with Macs, but I'm trying to help a friend (who dropped his MacBook Pro) recover his data files. I got the MacBook opened up and pulled out the drive. I have it connected via USB to a Linux box as an external drive. Linux sees the drive and I can go into Users/Joe but all the subdirectories have an "X" over the folder icon and when I try to open any of them, I get "Failed to open Documents. Permission denied."

How can I change the permissions on these folders?

Additional details

'sudo chmod' returns "Read-only file system" but when I run 'mount', it says: /dev/sdb2 on /media/Macintosh HD type hfsplus (rw,nosuid,nodev,uhelper=hal)

Also, I have my friend's password, but at no point am I asked for any credentials.

I don't believe, off hand, that linux can read/write to a journaled hfs+ filesystem.