Last updated: 6 September 2026
What this is
Muster is a macOS application written and maintained by Raphael Fiedler, Vienna, Austria. These terms cover your use of it.
Buying it
Muster is sold through the Apple App Store. The purchase is a transaction with Apple, at the price shown there, and Apple handles payment, invoicing and refunds. Apple’s Licensed Application End User License Agreement applies to the licence you receive.
Your statutory rights
If you buy Muster as a consumer in the EU, you have statutory warranty rights under Austrian and European law, including for digital content. Nothing on this page limits them. Where anything here conflicts with a right the law gives you, the law wins.
That includes the right to have defects remedied, and to a price reduction or termination where they are not.
Refunds go through Apple, who handle them under their own policy.
What Muster does not promise
Beyond those statutory rights, and only as far as the law allows:
Muster syncs with servers run by other people. It cannot promise that Google, Apple, Microsoft, Nextcloud or any other provider will keep an interface working, keep it available, or behave as documented. When one of them changes something, the app is fixed as soon as it reasonably can be.
Your data is yours, and I do not have it
Muster keeps your contacts on your Mac. I operate no server, receive no copy and hold no backup.
So I cannot recover your data for you. If you lose the key that encrypts your store, its contents cannot be decrypted by me or by anyone else. The app makes you write that key down before it encrypts anything, and it includes a backup feature that writes an encrypted archive wherever you choose. Use it.
A sync you approve can delete a card on a server. Every sync shows what it would change before it changes anything. Read it.
Your accounts
You are responsible for the accounts you connect and for having the right to connect them. Connecting an employer’s account may be governed by rules that are not mine to interpret.
Liability
To the extent the law allows, my liability is limited to intent and gross negligence. Liability under the Austrian Product Liability Act, for personal injury, and for anything else the law does not permit to be limited, is unaffected.
Not affiliated
Muster is not affiliated with, endorsed by or sponsored by Apple, Google, Microsoft, Nextcloud, Zoho, mailbox.org or Proton. Their names are used to say which service the app talks to.
Governing law
Austrian law applies, excluding its conflict-of-law rules and the UN Convention on Contracts for the International Sale of Goods. If you are a consumer, this does not deprive you of the protection of the mandatory law of the country you live in.
Contact
Raphael Fiedler, Vienna, Austria — mail@raphty.com