“Since I am the sole founder and shareholder, the 25,000 EUR are owed by me (with 12,500 EUR having had to be paid in at day of founding, and the remaining to be paid in the future).”
German non-profit law bars shareholders from taking profits and caps salaries. That makes Mastodon hard to sell to a buyer looking to squeeze it. It also leaves one founder as sole shareholder and CEO. The structure stops a sale. It does nothing about the bus factor.