Title is clickbait and inaccurate - they raised €550k at 100,000 users.
So they bootstrapped until 100k users (still a great achievement), but hardly to 4mil users as the title would suggest.
Even funnier: they forgot to mention all that sweet sweet EU and Austrian R&D funding money they received over the last couple of years for 'research projects' that don't deserve that title at all.
At least remove the Google part. Maybe just "How we grew to 4M users" since they didn't bootstrap. They got traction and raised money.
Also, their software is actually really helpful at thinking through ideas. I don't mean to knock them. But the title is wrong and takes away from their achievement.