An 'open letter' is unlikely to free Mr assange. It's interesting that when people are in jail, the most common thought of their supporters is that writing letters will make them going out of jail...
Statistically speaking, most prisoners escaped jails by defeating the inner security of the prison by various ways (tunnels, disguise, etc...) and this usually involved a net of complicity (prison administration, drivers, helicopters, weapons etc...) I'm afraid the same applies to Mr Assange ...
