I think the best way for you to go is to research and use 'open source software' for what you would like to do. This type of question will come up again and again, so I suggest that you spend some time reading up on open source software; understand what it means, its history, its pros and cons etc. But just to get you started, open source software is basically software that is not only free, but the source code has also been provided free of charge so that whoever uses it is free to amend it to suit their purposes.
There are a wide range of open source software available for almost any kind of activity that you can think of, so you often have to spend some time researching which one is best for you. In determining which open source software you should use, there are a number of things that you have to consider, including:
(1) What software the open source software is built on:
If your area of expertise is HTML/JavaScritp/PHP/MySQL, for instance, then it would not be helpful for you to choose a software built on Java/Oracle as you may not be able to amend it. If your hosting server runs asp you might not be able to install and run a php open source software on that server etc etc.
(2) Best for purpose
"Best" software can mean different things to different people. Some might want a complex and feature rich software, some might want a simple and easy to modify software, some might want one that has a very good user intercase etc etc... it is up to you to decide what is best for you but a good way to start is always to search forums for comments from people who have used these software products.
(3) License types: It is important that you choose the appropriate license type for what you want. You might find an excellent open source product but the licence type might not be ideal for you. There are several types of open source licenses ranging form the more restrictive GNU Library or "Lesser" General Public License (LGPL) to the very liberal MIT licence. I advice that you google this topic, but I have provided a few links that might be useful:
The last thing I would add is that in order for you to be able to understand and modify most open source software, you have to be technically competent to do so. The course you had with us is an introductory/beginner course and is probably not enough for you to be able to understand how to modify these software. On the other hand, there are certain people who have the ability to easily learn by themselves, once they have been given the initial grounding in software coding, as we have given you. If you are that kind of person, then you can use such a project as a way of improving your software coding skills.
As a starting point, I would advise that you Google "Open Source CBT software" and continue from that point. You will find many options open to you. I would like to point out that this application that we are currently using was created from an open source software called: question2answer.org. There were many similar software products to choose from so I had to do some research before deciding to settle on this