Welcome @AFDudley! Appreciate your question.
What other kinds of entities? I think of SourceCred generating two signals right now: cred attribution (who did work) and the grain balances (who paid for it). So I started with just thinking of cred-earners and grain-holders.
But if you reason through the social implications, you realize that the “founders” and “new contributors” will have different perspective and interests (as @s_ben does a great job exploring), so I think we need to enfranchise them separately, to avoid the new contributors getting marginalized.
In the long run, as we flesh out an economy of interconnected projects, the downstream users will have influence over their dependencies, since a lot of the value of a project’s grain will relate to the upstream “homage” flows from its dependents. But I think this is an external influence on a project’s governance, but I don’t see why they should get modeled as a first-party participant.
@mzargham, thanks for fleshing out all the different intersections between these groups! The categories you enumerated (and the example instances) make a lot of sense to me. I’m also very entertained by the idea that we can model computer aided democracy if only I can transform into an AGI 
.
Glad to hear that you think building a multi-stakeholder model will make the system more robust and responsive.
@s_ben, I super appreciate your post; thanks for writing it! You’ve done a really good job of exploring how there will inevitably be tension between the “cred elite” (founding class) and newer contributors. Your point about power corrupting is well taken too (it’s something I’ve observed directly in my personal lived experience).
I think enfranchising the “new contributor” class (with explicit governance power) can do a lot to ensure that their voice is heard and that they feel empowered down the line.
On a meta note, I think there have been some really valuable contributions in this thread, and likes 
don’t let me express how valuable some of the posts are. I wish we had boosting implemented so that I could signal boost these posts explicitly. 