The only full-fledged GPL Cocoa editor for GEDCOM 5.5 files (GenerationX) was last released in 2003: <http://sourceforge.net/projects/generationx/>
It looks unstable under Snow Leopard and would badly need a revamp.

Someone recently posted a proof-of-concept application (unrelated to GenerationX) on Google Code, but it looks like an unmaintained project:
<http://code.google.com/p/cocoa-gedcom/>

Is there any Cocoa developer interested in genealogy and willing to resurrect any of these projects? Or any other projects with a decent release cycle I am not aware of?

The Mac genealogy software market is dominated by pricy and feature-bloated proprietary solutions. A no-nonsense open source GEDCOM-compliant framework for Mac OS would be a blessing.