Software companies that include a denial of legitimate ownership transfer of their products in the applicable tos, whether by sale, trade or gift,  have violated the law. The most they can legally do is deny support on the qualification that such services are limited to the original owner by purchase contract.
Intellectual copyrights for software are currently a matter of intense debate, especially in the international courts. The Uniform Computer Information Transactions Act is not yet law, which means that the principles of "fair use" and "first sale" still apply.
One of the better known suits in this category involved Caere, the makers of Pagekeeper Pro. Caere filed suit against a customer who attempted to sell a used, legitimately purchased copy of their product on eBay, just as you have. The defendant filed a counter-complaint and won easily. So if eFrontier threatens to sue, throw a party. You've just purchased a winning ticket in the litigation lottery.