The work required to keep IA infrastructure operating is full time: these are full-time positions. IIRC they were at ~70 racks of stuff just in the California locations and apart from on-call and emergency response there's growth to keep up with, future planning etc.

There's no reasonable world where this is a few hour's per week volunteering like your local boat club. It's a Top 200 website, around the size of the Guardian newspaper -- never mind that Wayback is only a small portion of what they do. (Book scanning, inter-library loans, paid services for other GLAM organizations and governments etc.)

You should definitely apply and sign a contract. They should charge you money if you don't show up at 3am in an outage.

All it takes is one emergency and the volunteer person doesn't show up for the non profit to want to hire a full time person. This event has likely already occurred at Archive.