I will be getting a Mac G4 laptop, will post the exact specs when I get it, and I was wondering if it would be safe to install Ubuntu alongside OSX (probably tiger) and would the hardware (graphics, sound, HDD size) be enough?
As Apple is always ahead of the hardware curve I'd bet on it that it will work. I have a Mac that is 6 years old that I run the current version without any issues.
The only "trick" is to install http://refit.sourceforge.net/ which will allow you to boot from into Ubuntu.
Ubuntu has always been better than the other distroes when it comes to installing and recognizing OSX partitions.
I recommend you use mac tools to resize the partition to make room. I used gparted and it took for ever, like an hour, whereas the mac tool takes minutes.