A month ago, I found GenerationX, an open source Mac OS X GEDCOM editor. (GEDCOM is a standard genealogy file format.) Unfortunately, the version I found was very old. It was PowerPC-only and crashed on launch on Snow Leopard.
I took the source on SorceForge, fixed many of the compiler and static analyzer warnings and removed the expiry code.
You can find my fork on github:
Be careful — this is still beta quality.
If you can't understand it, it is intuitively obvious.