Subsonic: questions in open source ethics

So there's a great open-source project out there called Subsonic. It's a streaming media server -- it will stream your music and videos from your home server across the internet/network. It's easy, user-friendly, and has a number of apps for mobile devices.

There's only one problem. You install it, get it configured, then realize that despite being open-source, it's actually shareware. You get the base program, but can't unlock streaming video or mobile access features unless you pay the developer money. And despite him saying "you can donate any amount you want," he only gives you an unlock code if you pay him at least 10 Euro. These locked features are part of the open codebase, but just won't work until you enter an unlock code.

This brings up some interesting ethical questions that I've thought about for awhile. I have no beef with people making money off their software. But the fact that it's open source makes it interesting. Also there's the fact that the website talks about it being free (he doesn't talk about speech vs beer). But then if you read further, you find out that it's not all free (beer). None of those things are problems. But they do make for some interesting questions.

It's open source (GPLv3), so I downloaded the source, and bypassed the registration unlock system. Now I have the full product without donating. What I did was 100% legal. Was it ethical? Does it matter that the author wanted me to donate to unlock it? Does it matter that I felt deceived after I installed it when I realized that these features that the website talked about were actually locked away behind a paywall? Does it matter that the developer had to have purposely chosen the GPL license, so was in effect expressly allowing me to do this?

Let's take it a step farther. Would it be ethical for me to publish a fork that just takes his software and removes the registration requirement? More importantly, would it make me a jerk to do so?

It's interesting, because it's clearly legal, and it's within the general spirit of open-source. But it's also clearly ignoring the developer's request to receive compensation for his work. Is that any different than what CentOS does with Redhat?

.....

Personally, I think Subsonic is great software, so I have no intention of publishing forked code, or even publishing how I bypassed the registration scheme. I figure if the guy keeps getting money, he'll keep making good software. Even if I feel like the donation requirement is poorly worded/explained. But I definitely think it brings up interesting questions.