iOS-compatible open source .framework libraries
Om nom nom.
Because you can include these frameworks into either ARC or non-ARC projects and you don't have to worry about whether or not their ARC-ness matches your project's ARC-ness.
Isn't that what static libraries are for?
Yeah, you can do that too, but this way, you can see each library's header files neatly packaged inside the XXX.framework entry in Xcode's project sidebar. You don't have to add the headers manually.
Can't you just set ARC/non-ARC compiler flags per-file?
Please go get laid. Or buy some lottery tickets or something. Go nuts.