Thank you for your question @Tane and thank you for taking the time and care to read our proposal! =)
So answering your question, other than the hosting costs to keep the servers up and running, the overall maintenance that would be needed for the next 3 years, is if Arbitrum governance contracts change somehow and therefor we would need to update our indexers accordingly. For starters, that’s not very likely to happen, but if it does, we commit to update our app as soon as possible, because since we send daily notifications emails to our users, we need to have the correct data for the that next day email to be accurate.
Also, just as a reminder, our app is fully open-source on GitHub - proposals-app/proposalsapp
Thank you!