How to get out of a data use agreement? My project is based on data hosted by a different university than the one where I used to work. When I requested the data, I understood that the work (and cost) to extract it from the database increases with the number of items I wanted. I had no research funds at the time and therefore asked for a rather small sample, with an informal agreement with the director of the inistitute that the person extracting the data would be my collaborator and coauthor. 

Several months passed before I received the data and then the sample turned out to be too small to be really useful. I did not make another request as the data extraction process appeared so time-consuming. Instead, I moved on to work with other projects for a couple of years.

The data became relevant again when I started as a visiting researcher at this institute. Although I wasn't employed by the institute, I had direct access to the database and could download all of it in a matter of minutes. I expected that the person who extracted the first sample would be willing to collaborate on data classification and other things where he was an expert. Instead, he seemed hostile and would only answer to exactly what I asked, rather than make an attempt to be helpful. 

The most recent development is that the institute made most of this database and classification open for anyone to download. 

What should I do to get out of the original data use agreement? I feel trapped in a forced collaboration with a person with whom I'm not in speaking terms. I'm not in a position to renegotiate or entitled to any help from the institute, as it is not my employer.

I took this situation more seriously than anyone should, as my depression renewed and I went to psyhotherapy for nine months. That's telling something about the amount of time I have wasted with this dilemma.
This isn't a question that can be properly answered here as it may have legal implications that are local to the actual case. Don't make assumptions that your old agreement is null, just because the data became public. No harm no foul might not hold up anywhere, especially if lawyers get involved. 

You indicate that the director is a different person than the one who helped you. He/she can give you advice. The legal department of the institution can give you advice that should hold up. If your new work is truly independent of the old, make sure that they understand that. The other person may have no moral hold over you for co-authorship, but only an expert can speak about a legal hold. 

The question is likely too old to be of help to the OP, but future visitors may have similar questions, hence this very late answer.