If I buy the lite version and decide I want more features, can I pay the $10 and upgrade it? Also, I'm not sure what computer I will be using yet, is there a limit to how many times I can transfer the license back and forth between computers?

There is No limit on transfers when you click the Remove license button on the pc's eJukebox about screen before registering with the license on the new pc. The only upgrade option is $25 to go Pro.