I think CC is perfectly suitable for your CMS, Taco. You're just too scared it will be misused once licensed under CC, that's all.

But I think the main part that keeps you from going CC, is that you don't want someone else to grab your CMS and make money out of it by commercializing it. That's the NC-part (Non-Commercial) of the CC license.
Furthermore you could decide to prohibit Deritive Works, which prevents it from being modified and distributed elsewhere, under another name.
Last but not least, if you decide that Deritive works are permitted, the SA part (Share Alike) forces the makers to make it open source as well, so that others (you) can enjoy the adjustments they made.

There are numerous legal cases where CC licenses prove their strength, and that it is indeed a license where people can be punished for when disobeyed.

Please, be sure to attend the lecture of Marco Raaphorst, as he is going to tell about CC. I also recommend to read a copy of 'the kathedral and the bazaar', a paper that is written by Eric S. Raymond, and free to read online, here: http://www.catb.org/~esr/writings/cathedral-bazaar/. It explains why open source software works and why closed source doesn't (that well).

I don't value money that much. I do value the time I can spend on anything. To me, time is more valuable than money.

In that light the time I spent on my CMS is more valuable than the ideas I had. The code I have written is not only a result of those idea, but also a result of the enormous time I spent making it. It's almost like a child, if you know what I mean.

To be honest, I still don't know what I will do eventually. It might be open, or maybe semi-open. Maybe it's indeed like raising children: you just have to let go...

Unfortunately I can't attend Marco Raaphorst's lecture.