As some of you might have read (https://fmdev.filemaker.com/message/128129#128129) there is no possibility to codesign FM12v5 runtimes on Mavericks successfully with onboard tools. So there is no way to handle Gatekeeper or to produce an app for the Mac OS X appstore.
But a solution is now there. I worked together with Sam Rowlands from Ohanaware - many thanks to him - and finally he found a way to wrap and codesign a FM runtime app on Mavericks - this is, what he writes on his website:
Apps made with FileMaker Pro cannot be code signed. (They can with version 2.3 of App Wrapper)
I've just assisted an App Wrapper customer who is unable to code sign his FileMaker Pro application. I discovered that some of the Filemaker frameworks within the Filemaker Pro application are incomplete.
Download version 2.3 of App Wrapper, as it adds a Filemaker Framework fixing engine, where it will go and fix the problems with the frameworks, allowing Filemaker users to code sign their applications on Mavericks.
You can fetch a demo of Appwrapper here:
Sadly, although I posted this as a bug to FileMaker, I got no reaction at all from them. So we have to "repair" FM runtimes ourselves.