Ask HN: What are the cons of using an established name for a new SaaS tool?

Context: There is an existing open-source project with quite a big audience that has a name that I wish to name my new SaaS tool after.

They don't have ".com" domain or trademarks.

Their product solves a problem in a similar domain but does not have an overlapping user base.

I am not concerned about SEO – the SaaS tool I have in mind will not acquire users through search results.

What else is worth considering?