support for non-fix bounties and extra legal requirements

We are thinking about paying bounties based on the number of test cases in the pull request.
It means that there is a minimal and maximal amount of bounty for a given issue,
and the exact amount becomes known when the corresponding pull request is merged.

Is it doable by starting a campaign for the maximal amount, adding bounty for the minimal amount,
and just before closing the issue adding the rest by the same entity?

Another question is that the projects in scope are open source, but there are commercial versions with more or less with the same codebase. We would like to make it a requirement to sign legal paperwork so we can use the code in the commercial version. Is it okay according to bountysource policies?

The issue names no files, tests, or entry points. Start by determining whether variable bounty amounts and legal-paperwork requirements are supported by Bountysource policy, then define concrete acceptance criteria for each request before locating the relevant implementation areas.

Written by the indexing model from the issue text.