Is it legal to use logos of customers without their permission?
Startups almost always “beg for forgiveness” here. They put the logos up without truly asking for permission. That doesn’t make it right, or “legal”. Eventually, at least some of your customers will notice, and you’ll be asked to take it down.
Why do they care, you might ask?
There are several small legal reasons, but one big one. When patent trolls go to sue a tech company, they often also sue several of their largest customers for using the technology. They tend to sue the ones on the website. Those are easiest to find.
Once you realize this, how patent trolls work … you’d never really want to be on anyone’s website …