Are there some restrictions in the Apple Developer Agreement that prevent one from distributing the source for your app on a 3rd party website? I have always heard the argument that you can't distribute GPL'd apps because the source cannot be bundled, however, the GPLv3 (and v2) do not explicitly require this as the only approved means of source distribution. In fact, section 6 outlines several methods - through which one could reasonably see that the source code could be made available elsewhere, as long as there were notice within the app on where to retrieve it.
Agreed, however, that there are other licenses which are less restrictive on those that distribute object code.
As an app developer I find lots of useful code online - most of it is licensed under the MIT license, meaning do with it whatever you want (by and large)
If you want to make it so other people may use your stuff, just put it under such a license. That's what I do - please, share and use, here you go. There are no strings attached.
If I see the words GPL, or even LGPL, I stay far away from it. I don't want some nutcase to sue me years down the road when my software has become popular, just because I wanted to save an hour of coding time for the 1.0 release.
As someone who releases software under GPL and LGPL, and hardware designs under CC licenses, I don't see how anyone would sue you over a GPL license. Unless, of course, you took something from a GPL licensed software and then did not provide your users the same liberty you had with the source.
Whether or not one individual prefers copyleft (viral) or non-copyleft licensing is largely due to their intent - not to garner the maximum number of users, but to ensure that anyone else who might profit from their works affords their users the same right. And, if you really wanted to people to do whatever they pleased with your work without regards to your desire, you would've made it public domain, not MIT-licensed. You chose a license because you had a desire that the license enforced.
Agreed, however, that there are other licenses which are less restrictive on those that distribute object code.