GENERAL
This is discussed in my blog and comments there are welcome. http://petosoft.wordpress.com/2013/08/14/frosted-glass-using-core-image-and-glkit/ It still has bugs and I just edited it from the GitHub editor so it might not compile. But fixes should be obvious.
iOS8
Nowadays, you have UIVisualEffectView, which may be more suitable for you and is a supported Apple class. You may still find that you prefer to see all the moving parts and may find this view more flexible.
LICENSE
I'm serious about open source, the community and giving back and I love the GNU GPL and all that it has created. In that spirit, this code is licensed under the LGPL.
The way I want you to use it is this: download the class, build it, use it and don't worry, it's safe.
The only thing I ask is that if you improve or extend this class, that you tell everyone about what you've improved and share it around, like I did, even if you have copied the code into another class or renamed it. (To make it simple and avoid issues, don't include this code inside a different class that you're not willing to share.)
SUPPORT
Unfortunately I cannot afford to promise support or service level agreements on this code either so by all means comment, add fixes, test and contribute but I cannot promise if you have a bug that I'll drop my day to day work to fix it instantly. We all know how this works!
FOOTNOTE
I hope someone uses it and loves it.
Carl