[clarle]

I like the idea conceptually behind the license, but without an explicit definition of what competition is, it feels tough to use.

For instance, Micro provides a persistent form of key-value storage. If my product focuses on a very specific audience (say medicine), but also exposes a way for doctors to store arbitrary key-value pairs, could that be argued in court to be competition?

The definition of competition in the Polyform Shield license is never explicitly stated, and in fact, it specifically calls out that "Applications can compete with services".

Whereas the MIT and Apache license are pretty explicitly clear in what the terms of use are, Polyform seems to be fairly vague there, which is potentially something you wouldn't want for a legal license.