What is the past participle of the verb open?

I'm French and I'd like to be precise on the conjugation of the verb "open".
On this picture, I'd write "opened" instead of "open". Could you tell me more about why they have written "open"?

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Solution 1:

Because "open" is the simplest form of the word as adjective. "Opened" is more often used as a verb. So we say "Is the door open or is it closed?

Solution 2:

"Open" is correct because it's an adjective. An open world is a world with fewer closed doors (barriers), presumably.

But I wouldn't trust anything that guys says about his company's "mission."