I wrote my own library in C to do it. It is not open source. The big reason is intellectual property constraints, as I had to obtain access to the API under non-disclosure, so I couldn't legally open source it, even if I wanted to.
I can also do things like program the stick to have a user-defined CDROM partition that actually appears to the O/S as a CDROM device, instead of a hard drive, and so the partition is locked and can't be written or overridden. By doing this, there is no need for any drivers or to install any software ahead of time. The way I have it set up, one can just plug the same stick into a sun, linux, windows, whatever, and it detects what O/S you are running, then kicks off the necessary executables. I even support big & little-endian based operating systems and hardware all living together in harmony with a shared R/W partition common to all operating systems.
By taking advantage of the locked-in-stone serial number in the device, and unique ID that I put in every stick when I "manufacture" the device with a canned CDROM partition .. then I provide a mechanism that is effectively system and O/S agnostic, that LEAVES no footprint on the client computer, and nothing to install.
The read/write portion of the USB can be used for application data, programs, whatever, but part of the magic is in the CDROM partition which can include some code that facilitates verifying that any program that resides on the R/W partition hasn't been tampered with.
Unless something changed, TrueCrypt just isn't portable, and one can make a binary image of a USB stick and steal the code. They can't do that with my implementation.
In the interest of full disclosure, I am not trying to tell you to come to me and buy something. I would have to make major modifications and I am rather expensive, and I hadn't even considered selling anything along the lines of an API or object modules and headers you can link into your executables.
I just wanted to tell you what was possible, because I did it. Also, I ended up getting a patent awarded recently on this technology that I filed almost 6 years ago. (The patent includes additional protection against piracy, because I was more concerned about having a technique to allow somebody to run code on any computer, regardless of the operating system, without it being stolen even if they made a bit-level copy and RAM copy). The encryption was a means to an end not the end-product.
If you need a high volume solution, then one can come up with something that does not rely on TrueCrypt limitations, that requires certain USB flash devices that cost much less money, and can be deployed w/o any footprint. You will have to work with hardware vendors (who don't know squat about UNIX file systems, by the way).
