DisplayPort technically isn't royalty free - it's just that Vesa isn't charging for it. However, it may do so in the future, though having established a precedent, starting to charge licence fees and royalties may prove difficult.
Why give it away in the first place? To encourage computer makers to use DP instead of HDMI. This doesn't appear to be working too well.
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@Ed
DisplayPort technically isn't royalty free - it's just that Vesa isn't charging for it. However, it may do so in the future, though having established a precedent, starting to charge licence fees and royalties may prove difficult.
Why give it away in the first place? To encourage computer makers to use DP instead of HDMI. This doesn't appear to be working too well.