Which they adressed in the last paragraph of the linked page:

"Is it an Open Source License?

While the Climate Strike License violates the Open Source Initiative's canonical Open Source Definition, which explicitly excludes licenses that limit re-use "in a specific field of endeavor", we feel that as tech workers, we should take responsibility in how our software is used, and that the urgency of climate change cannot be limited by the ideological position of open source software. Instead, we want adopters of the Climate Strike License to take a bold stance in the fight to save the planet."

"the Climate Strike License violates the Open Source [Initiative]"

So it's not open source.

Then why even make the license? This is a useless virtue signal. If you want to help solve environmental issues, there are many actual ways besides trying to ban industries from using your FOSS.

From the page:

>> Is it an Open Source License? While the Climate Strike License violates the Open Source Initiative's canonical Open Source Definition, which explicitly excludes licenses that limit re-use "in a specific field of endeavor", we feel that as tech workers, we should take responsibility in how our software is used, and that the urgency of climate change cannot be limited by the ideological position of open source software. Instead, we want adopters of the Climate Strike License to take a bold stance in the fight to save the planet.