It’s your premier product/service launch, and a colleague (not a VC) invests money/time in it—do they get to put their company’s name on it too? Whereas I think it might make sense when it’s an established brand, in cases where the other company is also trying to get established, doesn’t it dilute your brand to do that? First impressions matter and I don’t trust that users would be able to properly distinguish between two unknowns introduced at the same time, even if it were explained somewhere on your site. But at the same time, if someone’s investing in you, I don’t know how I could tell them that they couldn’t do that without looking egotistical or inconsiderate. Any pointers?
Put them on the about us page as an investor. There is no reason to have it anywhere near your main marketing pages.
If your website is designed to get you customers, it should be designed to get you customers. Not to stroke your investors ego. Ultimately, they also benefit when you get customers.
Tack "Sponsored By" with their name. With the right design I think brand clarity could be achieved without any sort of length explanation.