While trying out various scenarios of embedding GlassFish in OSGi environment, I stumbled upon this issue. When the launcher classloader has simple-glassfish-api.jar and osgi framework is configured with same properties as regular glassfish, then I found that GlassFishRuntime.bootstrap() fails to find RuntimeBuilders. It happens because we don't configure system package to export org.glassfish.embeddable.spi package. Similarly, glassfish.jar bundle does not import this spi package as well.
This needs to be fixed in 3.1 branch if that branch opens.