I have a two part answer.
Is it worth bothering to upload the .mw files
Yes, upload the code. Upload all your "real coding" projects, too.
or should I just stick to my other "real coding" projects?
This is the more interesting part, and the answer is, "it depends." Any job hunter should have a library of material they can pull from, including stuff they know won't always be relevant. Keep a diverse portfolio, then select what you share with a given employer based on the specifics of the position and the value you can show. You don't want to spam every employer with a bunch of material that's not relevant, but you also don't want to send everyone the minimum common denominator.
In other words, it's better to be able to reference Maple in your cover letter with a link to your projects if you know the work is relevant to the specific position, versus not having a portfolio at all, or sending them a link that contains a lot of stuff that isn't relevant.
Maple is a pretty specific language, which means (as you're guessing) it won't be relevant for many pure, generic software development jobs, but if you're going after a job in that specific field, it can be a really great tool to showcase. Also, it can be helpful even in situations where Maple itself isn't directly relevant to be able to show that you can "think outside the box" and do work in lots of different tools, versus being a one-trick pony who only knows a single language.