I don't see this as an issue, personally. Part of their product is open-source, and part of it isn't.

In addition, their product can be used to help open-source projects with documentation, code running, etc.

When I read "Open Source" near the bottom, that's what I read (the we help you with your open source projects).

Also, any company is allowed to use names as long as they have an agreement with the company in place. Whether or not those companies use 1 of the company's products or all of them doesn't matter much. You see this a lot on Enterprise-oriented websites. Not all customers who leave case studies will use all the products.