There are two versions of NTFSDOS. The first is a free read-only driver which is their own code. The second is the full commercial read-write version, which uses the system's existing ntfs.sys driver with a wrapper.
Interestingly, if you're looking to repair unbootable NT/2k/XP partitions (or blag the SAM file by booting off a DOS floppy), the read-only version works on all versions of NT I've tried it on. Unfortunately, due to the reliance on the Windows ntfs.sys in the read-write version, one boot disk can't access all NT types (even actually amongst service packs).
Both are still available afaik, at sysinternals.com
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Interestingly, if you're looking to repair unbootable NT/2k/XP partitions (or blag the SAM file by booting off a DOS floppy), the read-only version works on all versions of NT I've tried it on. Unfortunately, due to the reliance on the Windows ntfs.sys in the read-write version, one boot disk can't access all NT types (even actually amongst service packs). Both are still available afaik, at sysinternals.com