It seems to me that is the crucial part. Even extending a core library (MY_* files) is not modifying the original work, it’s simply linking to it and including it in our own applications. To me, this means everything we do, unless it is modifying the core files, is free from the viral nature and we can do whatever we want with it.
And since the application folder’s contents are licensed AFL, that means those files can be modified and redistributed (which we all do with every app) and put under any license we need to.
Actually AFL does NOT mean you can put it under license you want to - Rosen also does not write that anywhere. Rosen also does not define if GPL is compatible to AFL and there is only one source at all claiming compatibility on the net.
Also seeing it from the GPL side does not make it compatible at all because either the package is GPL-compatible as whole or it isn’t. Having that one folder under AFL (even it might be compatible, which i doubt) doesn’t cut it for the GPL. Having it all under AFL might be different.
It has also been expressed a couple times here: OSL/AFL is more like the AGPL in terms of the ASP loophole. That means that if you provide services with your application written based on CI you might have to provide your source code to the users. Bye, bye business.
This (still uncommented) license change is creating a very uncertain situation for all CI users. Just this discussion might refrain potential interested parties from using CI at all currently. I hope EllisLab listens to all these concerns and voices from their user base and changes to a more compatible license.