I find that Openbox is probably the fastest graphical WM for PPC linux, but that takes some elbow grease to get up and running. If I could wrap my head around (and had time for) putting together a small distro to make it easy for others to install, I would jump on it. Other than having to set radeon.agpmode to -1, the video acceleration issues have all been eradicated with the radeon and nvidia firmware in the Ports distro of sid. Unfortunately, G5 support in sid is still VERY spotty.
Coreplayer is the secret sauce for OS X and video consumption on PowerPC these days. The huge advantage that it has over linux is >360p video on G4, at the very least. Mplayer and 480p webm video works great as well, while the downloads of such videos error out on me using youtube-dl under linux. I haven't yet tested 480p webm on linux (by moving such videos over), but my machines are packed away for my impending move back home (which is any day now).
As
@wicknix stated, browsing on a fast WM in PPC linux is a real joy. Midori is great for everything but videos (and secure browsing, as it's 3 years out of date. Videos have a blue hue issue), and Arctic Fox takes up the slack nicely with a mild performance hit on heavy pages. Once those pages load though, AF rocks.
I'm also running sid on my black Macbook 4,1, and it just smokes. Definitely worth a look on older Macbooks.
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I put OS 9 on mine using an image from macos9lives.com. Works great, especially with MacMAME and other emulators

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The majority of commands that you would have to use to install linux without a graphical install would involve apt (or apt-get, or aptitude, if you prefer those). It's more of a need to know WHAT you have to/WHAT you want to install. My sid HOW-TO thread is a simple guide on how to do so, but is for those who don't mind getting their hands a little dirty. I am also available to help in any way that I can

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Debian Ports sid has taken care of the GPU issues with the newest firmware. Most cards will have no issue, and have full acceleration out of the box. Really OLD cards (like the Rage 128) aren't really supported anymore, though. Ubuntu Mate 16.04 on my dual core 2.0 G5 runs great, and that has a Geforce 6600, so they've done some work with Nvidia cards as well.