The license has been criticized as not being truly "Open Source" or "free".
https://en.wikipedia.org/wiki/TrueCrypt#Licensing_and_Open_S...
Wikipedia lists it as "source-available".
https://en.wikipedia.org/wiki/TrueCrypt#Licensing_and_Open_S...
Wikipedia lists it as "source-available".
The security assessment is for the Windows version of TrueCrypt only. Which also answers your question, TrueCrypt is appealing because it works on *nix, BSD, and Windows. It is also free and open source. The Windows version is easy to use, has a nice GUI and actually works as stated.