Hi @cutalion
Thanks for your question here on Enpass Forums. We are really happy to see your concerns about the security of your data.
Yes, Enpass is not an open source software because of the nature of our business.
First things first, its the security of your data. Instead of our own proprietary code for Cryptography, we have moved to SQLCipher (which is an open source Cryptography Engine) and is being used in worldwide. You can read more about security-in-enpass here.
Being an offline software, your data is never stored on our servers and never leavs your system in unprotected way. You can verify this by using network sniffers on your device.
For more you can go through our Security FAQs here https://www.enpass.io/kb/mac-os-x/
Cheers!