Looks like you need the Enterprise license, since $5M or €5M in early funding is probably above the threshold of €1M/year in revenue-or-funding mentioned on Buy | Kirby CMS
See also “What does the revenue limit for Kirby Basic mean?” in the FAQ on that page.
Kirby licenses, whether the discounted Basic one or the full-price Enterprise one, don’t have a per-seat component.
Note that there’s a 20% discount right now until the end of the week: