Yes, they are without blobs. They come with Libreboot, a coreboot distribution without blobs, not vanilla coreboot.
Similar notebooks with Libreboot are offered by vikings.net, tehnoetic.com, and zerocat.de; minifree.org is the business of Libreboot's main developer and former lead, so buying from them directly supports development of Libreboot.
Their laptops have been gutted of the Intel Management Engine/AMD PSP, they ship with coreboot on them, and (I think) they're without binary blobs(?).