I have to agree with Berki on this one. It is absolutely ridiculous that eBay is enforcing LH's rules, from a legal standpoint.
As long as the sale of miles is not illegal under German laws, as I believe Germany is still the legal location of the program, eBay has no right to share the information with Lufthansa or listen to the instructions of LH.
I wonder if they have any contractual relationship - and because of this eBay follows LH instructions. Are there any kind of joint marketing programs between the two of them?