MetaMask Flask (purple fox) is the canary version of MetaMask for developers. You can use it to build and test Snaps. It has experimental APIs that have not been released to stable yet (orange fox). You can invite users to test your Snap with Flask, but they should not use it with real accounts or funds. It is an experimental testing environment that is not guaranteed to be stable.

Can I just use Flask to distribute my Snap?

You should not encourage users to install Flask. It is not guaranteed to be reliable. Also, if you do not submit your Snap for the allowlist, it will not be listed in the MetaMask Snaps Directory, so users will not be able to find your Snap.