Interesting!
Given the spokes were rusty I would have replaced them, to avoid breakages in future.
Doing that though kind of detracts from the benefit of them being free! When I get free stuff, usually off the street or out of a skip, I just take the view that since I haven't paid for it to begin with, any useful life I get out of it is a bonus.
Personally I reckon that only high quality rims are worth the expense and effort of re-spoking and when it comes to secondhand cooking grade components that are already part-worn, you might as well just finish wearing them out without further expenditure. I will salvage axles/cones or hubs out of totally scrap wheels though if they are still useable.