After conversations with HLF, ConsenSys and other Besu maintainers, here is an updated proposal for the incentive program which seems to align with everyone's interests: https://notes.ethereum.org/@timbeiko/besu-cip-proposal-4. Note: the proposal is still a WIP, and isn't a final legal/grant agreement. The goal is to use this to get alignment at a high level across everyone and then draft a proper agreement.
Apologies for not posting the proposal directly in the wiki, but it seems like markdown isn't natively supported.