The bandcamp page links to ewanmaccoll.co.uk which looks official (has a 'Shop' linking back to the bandcamp page among other things). Looks legit to me.

It's certainly all very visible; I'd be very surprised if MacColl's estate is unaware of it... quite apart from anything, it would be a rather bizarre activity for an aspiring bootlegger to engage in, given the massive amount of time it must have involved for limited returns. Plus loads of the albums on there would not fall under age-related copyright expiry anyway (70s and 80s albums).