There is nothing special about truecrypt formatted encrypted volume.The only thing interesting is the format of the header used to store information about the properties used to create the volume and necessary to open the it.
cryptsetup is a front end to dm-crypt,an infrastructure in linux kernel that deal with block device encryption.cryptsetup just parses truecrypt header for volume properties,the hard crypto stuff is done by the kernel.
tcplay does the same thing,it just parses the truecrypt volume header and the hard lifting is done by linux kernel in linux and bsb kernel in BSD systems.
In both two projects,the crypto stuff is done either by crypto routines in kernels or by libgcrypt or openssl.
zuluCrypt is just a front end to the two projects above.
None of these projects do crypto stuff themselves.
It should be possible and to some,"trivial" for windows or OSX tools that deal with block device encryption to support truecrypt format.I think this will be a better use of the resources.
tcplay[1] is a BSD licensed CLI tool that can be used to create and open truecrtpt volumes.
cryptsetup[2] is a GPL licensed CLI tool that can be used to open truecrypt volumes.
zuluCrypt[3] is GPL licensed CLI and GUI tool that can be used to open and create truecrypt volumes.
arch linux users can get zuluCrypt from[4]
[1] https://github.com/bwalex/tc-play
[2] http://code.google.com/p/cryptsetup/
[3] http://code.google.com/p/zulucrypt/
[4] https://aur.archlinux.org/packages/zulucrypt/