Lets see:
These alternatives are not as powerful as Flash. But you are right, it'd be better to use one of them. Anyway, I haven't learned that at college and, the most important point is the following:
Being open source does mean that its source code is available for everybody to view, edit and redistribute it. The fact that Adobe Flash is not open source does not mean that the works created with it can't be open source.

If you want to learn how to work with any of these softwares, go ahead. I can't. It should be really nice to do all my design work with open source alternatives, but just I can't: From alias, inventor, catia or solidworks to flash.

EDIT:
I agree with you with all you have said, it is rather better to use open source licenses. I will never give my money to companies such as Adobe. At this moment, due to my experience and free time, I can't manage to work with an open source alternative. But this doesn't mean that the work I create will be propietary work.