The meaning is a bit different. You might say "This course appeals to me" or "I like the look of this course" before you choose a course, but not if you're actually doing it.
"I like this course", on the other hand, suggests that you are already doing the course and enjoying it.
Well, with "podoba mi się", you can be already doing this course, but I guess you can just like the idea and the topic of it - before you decide to start.
Are there definite circumstances in which you would chose between "lubię" and "podoba mi się" or are they interchangeable?
"lubię" is more general, the general feeling of liking something. So it's rather "I like horses" (general) than "I like the horses" (which suggests some specific horses).
For "lubić" you should have some knowledge, some experience with what you like. It's not a first impression.
"podobać się" is often about first impressions, it's also often about aesthetic impression. For example you can say "Lubię cię" to anyone that you like, but "Podobasz mi się" is rather "I find you attractive". Although in a proper context, for example when the person (probably a person you don't know too well) just made some very witty remark you can say "Podobasz mi się" to mean something like "You seem like someone I could get to like". But let's say that's still a bit risky.
Also compare: "Lubię ten film" (I like this movie = I watched it several times and it's one of my favourites) vs "Podoba mi się ten film" (I am watching it right now for the first time and I think it's really good).
Therefore "Podoba mi się ten kurs" suggests that I'm rather at the beginning and my first impressions are good, while "Lubię ten kurs" is like "This is one of my favourite classes, I enjoy taking this course".
Grammatically it sure is closer and it helps understanding how the Polish sentence is constructed, but I have doubts if it means the same thing. OK, in this specific sentence it seems like a reasonable thing to say (ergo: added now), but try going to the store and saying "This pillow pleases me" after taking a look at a pillow... that sounds less probable, I believe.