Development stores can use StoreForms free. Shopify automatically converts any subscription on a dev store into a test subscription — no real money moves.
Setting up a dev store
From your Shopify Partner Dashboard, click Stores → Add store → Development store.
Install StoreForms from the App Store as usual.
Subscribe to the standard plan — the charge appears in your admin but is marked as a test, and you won't be billed.
Caveats
Test subscriptions don't carry over if you transfer the store to a paying merchant.
All features work identically — this is the right place to evaluate StoreForms before deploying to a production store.