Ask HN: Legality of using previously open source data?

To protect the innocent/guilty, I won't name the company here.

1. Need a data source, which previously was open for commercial use, for one of my MVP features

2. After a merger, company now offers a "no-cost" license to use so long as proper attribution is given and brief approval process is completed. Have been talking with them off/on multiple times for 12 months to gain access. Seems I am too small a company for them to really pay attention to regardless of their public statements re: access. I have even asked them to come up with a "per api call" fee that was fair to both parties (until I can get bigger and pay their ~$5K average minimum fee) but no luck so far.

3. Came across an academic study on github which used this company's data from 1 year ago.

Am I allowed to use the old data set for my internal research and commercial purposes? I only want to do the right thing.

Thanks in advance!