DP is very much not free. VESA themselves is happy to tell you that DisplayPort is excluded from their list of free standards, and the leaked copies of old standards are stamped with a "distribution to non-members is prohibited" notice on every page.

I'm not sure where that misconception came from, but it really needs to stop at some point. The best thing to say about VESA is they're slightly less bad than the HDMI Forum. But only by so little.