With capital gains tax in Aus, it's a bit complicated. The wording on the ATO's site is ambiguous, and I suspect it's deliberately ambiguous, though it's looks like they've made things a little clearer recently.
They always say Bitcoin and other instruments which have the same properties. Okay, no other asset has the exact same properties as Bitcoin, so are we to say that these rules don't apply to Steem? Probably not, but there's no clarification as to how different something has to be.
It does say "Cryptocurrency may be a personal use asset if it is acquired and kept or used mainly to purchase items for personal use or consumption." So your intention when you acquired the Steem or SBD comes into it. Just because you're using it to buy things doesn't rule out the ATO coming around and saying "you acquired it for a different reason, and therefore you must pay." I don't think they'll do that, because it would be too much of a headache for them in many cases... but they might.
Then there's the fact that, with Steem, you're generating an income, not through capital gains. That means they might even want to double tax people, income tax then capital gains when it's sold or trade.
Then they expect you to keep all kinds of records, the dates, value in AUD, purpose of transaction. They want people to do their homework for them. It sounds like they have another thing coming.
The rules might change before the end of the financial year, considering they did open it up to the public to get feedback. Though really, I suspect not many people did give feedback because they don't want to put a target on their own backs.
So much FUD now