Use Docker Pro subscription inside a company that uses an open source alternative

As far as I know, yes, you can pay for your Pro subscription and use it for commercial projects at the company.

Unfortunately it is hard to find a clear list of what you can or can’t do with a subscription and I am not a Docker staff member to give you an offical answer, but I quote from the FAQ:

I work at a large company (5,000 employees, $2 billion annual revenue) and have been using Docker Desktop for free. Under the new subscription terms, do I need a paid subscription to continue using Docker Desktop?

Yes. Commercial use of Docker Desktop at a company of more than 250 employees OR more than $10 million in annual revenue requires a paid subscription (Pro, Team, or Business) to use Docker Desktop. While the updated terms for Docker Desktop are effective as of August 31, 2021 there is a grace period until January 31, 2022 for those that need to transition from a free to a paid subscription to use Docker Desktop.

I highlighted that it says you can have Pro licence which is for individual developers.

Also notice the conditions:

more than 250 employees OR more than $10 million in annual revenue

So if you are working for a smaller company with less profit, you may continue to use Docker Desktop for free. But I guess the company wanted to use an alternative because otherwise they should have paid for Docker Desktop.