See for instance here. Currently, o.a.l.l.util.ProviderUtil has a findClassLoader() method that depends on using the thread context class loader (TCCL). Now this method may work in certain environments, but once you're in an OSGi environment, class loaders are far more modular thanks to each bundle getting its own class loader. The thread context class loader is oftentimes not the correct one in such an environment.
I'll do more research on being compatible with OSGi without depending on OSGi. In the meantime, this ticket will have to do.