How is that a problem? I also rent 2 paid servers and what I'm paying for is practically comfort - the servers are always online and everyone can join them when they want (they're purpose servers for organized events) and I don't have to be online all the time to keep server online,while the free server is basically a temporary server,where you can meet with friends and race together. Or host some semi-spontanious events. So if the devs can keep the whole network alive with income from the paid servers,then I don't see the reason to ban free servers - not allowing the chance to have free servers would affect online activity and might have big impact on racers base in future.
LFS is not a huge profit commercial project like iRacing - LFS devs already have shown they're not doing this to get very rich,but for the passion of creating the best racing sim they can while earning living with it.