You can accept a gift. It's also possible for someone to give a grant. But I'm not sure how they would work out in case of open source. I know that people write books using a grant.
The thing about gifts is that the person wishing to give one needs to ask proactively how to do it and then you can give e.g. your bank account details to that person only. You cannot put your bank account or instructions how to ask publicly available. Years ago we asked about this from the authorities when I was in a non-profit and this was the answer.