Incorrect OSGi bundle header
In your manifest I notice you have the following two lines, which do not line up:
Bundle-RequiredExecutionEnvironment: J2SE-1.5 Require-Capability: osgi.ee;filter:="(&(osgi.ee=JavaSE)(version=1.6))"
A BREE of Java 1.5 is incorrect because snakeyaml contains java 1.6 bytecode and therefore will not work in earlier execution environments.
Since the introduction of "Require-Capability: osgi.ee" the BREE header can be considered obsolete and could be removed entirely. This would avoid these two headers falling out of sync again in the future.
Edit: I should back up my claims with references! Please see OSGi Core Spec r6 chapter 126.96.36.199 where it says that the BREE header is deprecated. But actually it has been deprecated since at leat OSGi Core Spec r4.3, a "long time ago" :-)