A reader worries:
Do you have more information in the "copyright reasons"? Nobody wants problems with the big red A company.
There is a difference between LT-Extender from Germany and the LT add-ons from Australia.
I am under the impression that LT Extender
modified the code in AutoCAD LT, which contravenes copyright [see correction by Torsten Moses in the comments]. In contrast, drcauto intercepts Windows API calls made by AutoCAD LT, which is perfectly legal in Australia. (Microsoft found this out the hard way when it lost a law suit against an Australian company making add-ons for the XBox.)
Autodesk doesn't like what drcauto does, and so makes the API call interception process more difficult with each release of AutoCAD LT.