Is pwSafe open source?

No, the source code of pwSafe for iOS and macOS is not publicly available.

Instead of trusting on a single developer security knowledge, pwSafe borrows all its encryption code directly from the famous Password Safe open source password manager.

Password Safe has been originally created by security guru Bruce Schneier and nowadays is maintained by Rony Shapiro. Since it has been around as an open source project for more than two decades now, it has been extensively reviewed by many experts.