Glass (especially borosilicate glass) is easy to use and work with because it can be heat sterilized/sanitized, but if you take care with sanitation, there is no reason you can't use something cheaper and more readily available, it just needs to hold the volume of wort, have a flat bottom and have a cover over it.
So the jar should work fine*, as would a demijohn or even a cheap-square-plastic-container or even a new/clean laundry-bucket ($0.87 from Bunnings today).
*It's hard to tell from the picture, but the jar might have a curved base, which makes positioning the stir-bar difficult, but with (lots of) trial-and-error, you should be able to get it to sit right - it's the trade off for using a cheaper jar and not a flat-bottom flask (KegKing sell 5L flasks for ~$30 which is very cheap compared to elsewhere).