Hi, here is a patch to fix "can't paste INTO upgraded version from every program - ID: 3297698". I'm not sure if 3.0 is ready for prime time so I'm also including the fix for 2.1, which has identical code.
The patch also fixes "Paste doesn't work when zoomed in - ID: 3136741" so pasting vector art also works while zoomed in.
I fixed "Paintbrush silently saves .tiff file as a PNG without renami - ID: 3288718" while I was getting the feel for the project so am including that fix as well, since it was a simple one-liner.
Tested on 10.6 Snow Leopard and 10.7 Lion on Intel Mac Minis. I don't have access to 10.5 at the moment but the patch should work on it since it's converting to pixels through an NSImage.