Frank and candidly straightforward / Generous and kind / Emotionally receptive

Someone who takes advantage of any opportunity to advance their own situation, placing expediency above principle.

Suitable for some particular purpose. / At a convenient or advantageous time.

A person who opens something. / A device that opens something; specifically a tin-opener/can-opener, or a bottle opener. / (in combination) An establishment that opens.

completely open / having no laws or law enforcement / unsettled or unresolved / vulnerable or unprotected / (sports) without the presence of opponents nearby

In an open manner, visibly, not covertly.

(grammar) A compound word with spaces in it, for example, high school, school bus, or science fiction.

(mathematics, physics) A differential operator,denoted ∆ and defined on ℝⁿ as 𝛥=∑ᵢ₌₁ⁿ(∂²)/(∂x_i²), used in the modeling of wave propagation, heat flow and many other applications.

A house habitually kept open to callers. / An event, often in one's home, at which there are few restrictions regarding who and how many may attend.

(sometimes attributive) Creative work that others can freely and legally copy or modify.