Microsoft has quietly been recruiting iPhone developers to create applications to run on its upcoming Zune HD media player. John Gruber of Daring Fireball reports that following a brief note he posted on the new 16GB and 32GB touchscreen media players, he received an email from the developer of an iPhone Twitter client, saying that he had been contacted by Microsoft and offered “a bucket of money” to port his app to the Zune. The developer in…