There are no risk in that, you can for example give them a upgrade code / voucher code witch is totaly anonomius (how's that spelled?) .
They would never get any info about the one that gave it to you So you are safe on every way.
Or do you mean, the chance of getting a lisence from the people on this forum? If so, the chances are low, so I wouldn't expect that, sorry.
You have no control over the other person's driving/forum posting so they could ruin your online reputation and get you banned from the LFS servers and/or forum for crashing or being a dick.
The online reputation is a rather minor risk. The two main risks are: gettting caught and banned, as License sharing is forbidden, or, even mroe mean, the one you give your info to could just change your password and that's it, you ain't gonna get it back.