KeePass is open source. There are ports for every major OS. I used it on my android devices, for instance.
KeePass basically only works well on Windows and you have to trust all the other implementations that make it pseudo-crossplatform.
You mention "open-source" so much one would think its a weapon.
Uh, except it's Windows only? Sorry, I use 1Password only on my iPhone as if it were a hardware authenticator. No problems.