You can earn LSK not only by voting for but also by supporting, which can generate passive income, Lisk Network is funding multiple projects from newly created coins. If you want to receive free LSK you need to run lisk-network-reporter along with lisk node and with each node you run and you need to specify Lisk address as INSTANCE_NAME in lisk-network-reporter config. Each node you add needs to have different Lisk address. After few hours this address should be listed in statistics with "fake" balance of (1.5mln LSK / number of payable contributors) which is reward for supporting Basically running lisk-network-reporter is giving you vote power of (1.5mln LSK / number of payable contributors) on reserved 1.5mln LSK vote weight to support If more people will contribute, reward per one will decrease. If you are node operator and looking forward to do the same, support, please check github repository.
If you want to keep receiving revenue by supporting Liskstats you need to keep track of all new Lisk releases and make sure that you always run latest version of Lisk. Only latest official version will receive reward.