Almost certainly not. The on-disk formats for RAID are, to say the least, not formalized. If it's using standard Linux RAID, maybe you can mount it under a Linux system, but the odds that you'll find software that can do anything as complex as turn that into a non-RAID filesystem in-place are probably zero. Think about it, that's an incredibly difficult task - you're taking however many TB of data that's spread across four disks and trying to get it into a fresh filesystem when the largest you can make is the size of only one disk. Since it's JBOD, you can't even cut a disk out and use your array degraded, so you're probably limited to copying.
Possible solution: if your DAS supports expanding a JBOD configuration, you can half-populate it, copy all the data, and then add the remaining disks. Other than that, I think you're gonna have to find a friend with 4 TB of storage you can borrow.