In a statement to developers on its website, Apple said they put the NDA in place because the iPhone OS includes proprietary Apple software they wanted to protect.
"However, the NDA has created too much of a burden on developers, authors and others interested in helping further the iPhone's success, so we are dropping it for released software," the statement read.
Developers will receive a new agreement, sans-NDA, covering released software within a week or so. Unreleased software and features will remain under NDA until they are released, according to the statement.
Apple also thanked everyone who provided "constructive feedback" on the issue.
The full text, after the jump, and an update.