Ask HN: How to open up side-project to potential partners

TLDR; My side-project has attracted a couple of devs looking to contribute (pro-bono). It will most likely remain a side-project, but has a small chance of gaining traction and becoming a "thing" (product? valuable resource?). How do I trial and/or on-board these people to help for free without jeopardizing my stake (hours worked, pride of creation/ownership)?

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I created a side-project (to learn a web technology, as I'm a non-web developer) and to scratch-my-own-itch in the sports space. Embarrassingly, I've spent 3 years on it now (sporadic hours, several breaks) and gotten it to the point where it's live and shared with a few people in that niche. The feedback is that the concept is novel, useful, but that the website needs work, especially the design (I fully agree).

I expressed interest in getting help on that front and I've gotten some offers to help out. Although I'm interested in seeing how these people could help out, I'm not sure how to best on-board them.

Part of my problem is that although so far this is clearly a side-project, I admit to having a small hope that it could become something more. I've already had minor interest expressed by a sizable player in the space that they like the idea and are considering doing something similar themselves (which could just mean doing their own version of the same idea - there's nothing proprietary about it).

Whether it's warranted or not, I feel some pride of ownership over this project (and have invested many hours), so I'm wary of letting someone else on-board with no stipulations, entering a grey-area in terms of ownership. Don't get me wrong, I want outside help and eventually a co-founder/partner (I know; it's a side-project), but that decision should be made at a later point with more information.

Some would just say to open-source it and be happy with any and all help that you can get, but I'm not there mentally (pride, desire to steer the vision).

Advice on how to proceed?