What is the name of this yellow / orange fungus?
Most fungi need to be studied under a microscope to determine a species. I think this belongs to the genus of Pholiota. I couldn't find an English name, if I translate the Dutch name, it would be 'Bundle mushroom'. This name refers to the fact that they always grow in groups, usually on (dead) trees or trunks.

At first look thought this was a Honey fungus, but these are parasitic so usually don't grow on dead wood.