Terms

Last updated 7 August 2026.

The software

UMSH is free and open source software, dual licensed under the Apache License 2.0 and the MIT License, at your option.

It is provided as is, without warranty of any kind, express or implied, including but not limited to the warranties of merchantability, fitness for a particular purpose, and non-infringement. Nobody involved in this project is liable for any claim, damage, or other liability arising from the software or its use. The licences say this at greater length and in more careful language; they are what governs.

This is experimental software

UMSH is a technology preview. The protocol is unfinished and changes without regard for compatibility. Firmware may fail, messages may not arrive, and an update may leave a radio needing to be reflashed before it works again.

Do not rely on UMSH where a failure to communicate would be dangerous. It is not suitable for emergency communication, for medical or safety-critical use, or as anyone’s only way of calling for help. Carry something you trust instead, and treat this as the interesting experiment it is.

Radio regulations are your responsibility

UMSH runs on radios that transmit, and transmitting is regulated everywhere. Which frequencies you may use, at what power, with what duty cycle, and whether you need a licence at all depend on where you are and what you are doing.

You are responsible for operating within the rules that apply to you. Nothing on this site is legal advice, and the fact that a setting exists in the firmware does not mean it is permitted where you live. If you operate under an amateur licence, the usual conditions of that licence apply — including, generally, that you may not obscure the meaning of your transmissions, which is why the protocol offers a mode that authenticates without encrypting.

Hardware

The boards this site describes are made and sold by other companies. Links to them are provided because they are useful, not as an endorsement, and no affiliation or partnership is implied. Your purchase is with the vendor, on their terms, with their warranty.

Flashing custom firmware may void a warranty. It can also, on some hardware, leave a device needing recovery steps that are inconvenient or impossible — the flashing instructions call out the boards where that risk is real. Do it knowing that.

Trademarks

Product and company names on this site belong to their respective owners and are used to identify the hardware and software being discussed. Meshtastic, MeshCore, and Reticulum are the projects UMSH is compared against; those comparisons are our own reading of public documentation and source code, are not endorsed by those projects, and may contain mistakes. If you find one, please report it — the comparisons are meant to be accurate, not flattering.

This website

The content of this site is published so it can be read, quoted, and argued with. The site is provided as is, with no warranty that it is accurate, complete, or currently true — the project moves quickly, and pages will sometimes lag behind it.

Changes

These terms may change. The date at the top will change with them, and the history is public in the project’s git repository. Continuing to use the software after a change means the new terms apply.