Puzzling - just wondering if what's called blackcurrant in the US is the same as the British ones (Ribes nigrum) as the only time you'd plant that close here would be if you were lining out cuttings. Each mature bush will need at least four feet with space between for you to move between them, ie 5 feet apart.

Sorry about the wait, but I was waiting for one of the members that live where Black Currants grow to answer. It looks like I'm going to have to do the best I can with my general knowledge.
A foot apart is way too close, as you guessed. It should be worth while moving them, as long as you have a place to put them. If you can list your USDA climate zone, and/or the State and nearest city, I could be more specific, but in most parts of the country, the best time to transplant is in the early fall, when the air is cooling, but the soil is still warm enough to encourage new roots. In areas where the soil freezes deeply, frost heaving is a danger for plants transplanted in the fall, so spring is a better bet.

Sorry, Stera! When I posted, no other answers were showing! Apparently I spent too much time laying out my ignorance. :)