Why is there no uptime for ARC-1?
ARC-1 runs on your own machine over stdio — there is no network address to reach, so uptime cannot be measured for it by anyone.
Is ARC-1 open source?
Yes — it is published under the MIT licence, written in TypeScript, 147 stars on GitHub and 2 open issues. The source link is on this page, so you can read exactly what it does with your data before you connect it.