It may be proprietary but it's developed by Tuxera, the same lads who created and maintain the NTFS drivers for Linux.
I'll do the former, as I always have.
By the way, a cool quote from the agreement preceding the download page:
>3. RESTRICTIONS: You agree to NOT: (a) disassemble, reverse engineer, decompile, or otherwise attempt to derive any source code for the SDA Software from executable code;
This should be quite alarming. They insist that we format SD cards with their tool, but they don't want us to know what the tool does.
I will not be the one reversing them, but I checked it is possible to download these through tor, and recommend downloading them that way to prevent potential trouble.
The hashes for the files I obtained are:
SDCardFormatterv1.0.2_Linux_ARM64
MD5: 2CF66295A29C5F496A489074CBC42CFA
SHA1: EE06C0C6834EB9F53E66343A7CFDB95FCCB5FF66
SHA256: 8695A0F441129845136AFEE01D94D6DBCCBE87BA7C904F045F2AF0613F9A1978
SDCardFormatterv1.0.2_Linux_x86_64
MD5: 459A698C3961BACA8103173B3CDA7173
SHA1: C28EFFDF05FF186E56C57476C2794CC7A7AE3AF0
SHA256: 3D961085954ABEB764265184A92C1114AA4CEF9CF12CA3C3337B6B63E0DBE0FB
Depending on where you live, this might have no legal effect. Some jurisdictions allow explicitly for reverse engineering & co. for different purposes (e.g. research, interoperability with other systems, etc.).
Would be an interesting project, I have no idea how you could reprogram them though.