And I don’t want people to work on Lemmy whose goal is to earn a lot of money, but those who are passionate about it.

How is that any different from employers that offer unpaid internships or a clients that ask newbie photographers to “work for the portfolio”?

No one is talking about “a lot of money” here. Whether you want it or not, you are expecting to get people to work for you (and you can call it a “co-op” all you want, whoever decides who-gets-how-much is the actual boss) for less than what they can get in the job market.

I even had to tap into my personal savings at times to continue.

Yeah, and this is a sacrifice that you chose to make. Which is totally fine. I also took some time to work on my own open source project long after the grant money was gone. I just don’t get how you think it is reasonable to ask others to do the same.

The moment you factor in the costs of employment benefits (to cover their vacation time, sick days off, fund their retirement, health insurance…) and taxes, the 4k€/ brutto quickly becomes 2k€ net.

I just hope you understand you won’t be the one determining what is “more than enough” - the market is, and the market is paying a lot more than 25k€/year for any decent Javascript/Rust developer. If you have people that live in areas with low cost of living and are okay with being severely underpaid for some higher purpose, then maybe you can pull it off. But it’s going to be basically impossible to find good people willing to stay for the long run with that attitude.

28k€/month is not enough revenue to keep all the people who are working on Mastodon. Donations can only work if we assume that there will always be a constant flux of people willing to work for free, dealing with all the unpleasant things that most FOSS developers rather not do.