I will have to kind of disagree with the above posters. It probably won't be a problem, but be prepared for it to possibly be a hassle, and think about preparing for that now.
My story: I took 1 semester of English at Vassar as an undergrad, which filled the school's req. I was a drama major, so I then took a two year sequence of dramatic literature classes, and also a dramatic literature seminar, in which I churned out a literary analysis paper equivalent to many English major theses. I enclosed notes explaining this with my secondaries to all schools, but a couple STILL wanted documentation from Vassar saying that the work I did could be considered equivalent to a year of English. For one of them, the letter I procured from the head of the Drama Department wasn't good enough - I had to go back and get a letter specifically from the English department. This held up my file being considered 'complete' at at least two schools, and as we know, being pushed back in the queue is bad.
So, I would advice you to think about doing the online course carefully, and if you go ahead, make sure that someone at some school will vouch for it, and if they will get it in writing BEFORE you start your applications.