I've burned my stainless steel macchinetta. Is it still safe for use? I accidentally put my macchinetta on the stove with no water in it. A few minutes have passed until I realized what I have done, and in the mean time the pot has overheated, started to smell quite badly, and it's bottom has received a (permanent?) brownish hue.

The pot is stainless steel (bialetti venus model), but I don't know what the inner coating is made of. In terms of toxicity, is it safe to continue using it?
Yes, it is perfectly okay to overheat stainless steel.

You can clean it by boiling soap water in it. Here's a link

You should replace the seal (the seal should be replaced ever so often anyways).