Their response:
The team that made dataroom has stated that they did not use any of papermark’s code and that dataroom was made from scratch with inspiration from existing document sharing softwares, and that this post’s allegations of us stealing code are false. [...]
The screenshots clearly show they copied whole pages verbatim, both design and texts. The founder, Nico Laqua, basically responding with "we didn't copy _code_" and not taking any responsibility says a lot about his and his company's moral code. It might not be enough to get sued. That doesn't make it right.