There are perfectly legitimate uses for the likes of nLite, vLite, etc.:
1) Slipstreaming, particularly things that don't slipstream well by conventional means (i.e.: Internet Explorer 8 and its hotfixes, Windows Media Player 11 and its hotfixes, etc. into Windows XP install).
2) Combining multi-CD installs to one DVD is another (i.e.: XP Media Center Edition).
3) Automating the installation of the OS beyond the parameters of winnt.sif (or the answer file used in question).
In fact, vLite is fine with Microsoft as long as you download the Windows Automated Installation Kit (WAIK, same thing used to create Windows PE discs).
I get that there are Microsoft-supported methods for slipstreaming most things (i.e.: hotfixes, Service Packs, some drivers) that don't involve the "Lites"--usually by using the command line and switches after the .exe or .msu file and specifying the location of the source files, which are typically copied from the installation media to a hard drive location...
I don't think having two Windows installation sources on one DVD alone is illegitimate in and of itself. In fact, it can be done with Windows PE and some scripts. If it is, then mapping a network drive to multiple installation sources at a company with legitimate volume licenses/MAKs/KMSes of XP/Vista/7 would be illegitimate. If anything, it's a perfectly legitimate option for deployment in a business.
If the "Lites" are used for illegitimate use, then it's because the user already has a non-legitimate product in the first place. If the OP is using pirated keys, then of course it's illegitimate (and using even one of those sources by any means would be). The use of a "Lite" alone does not automatically make the product illegitimate, unless, somehow, the user reverse-engineers the installation source to a degree that violates the EULA?