Hi,

this is a very interesting question. I'm not sure if anyone here can answer that in the specific context of islam - you had better ask a religious authority.

I'd guess (but I'm not muslim) that islam does not allow you to demand interest when lending someone money. You might argue that in steem you don't lend anyone money, so whatever steem gives you as payout may not be interest in the sense of islam.

The steem whitepaper talks about interest in connection with "steem (based) dollars". This interest is accrued automatically if you have an SBD balance, and it is automatically paid out when your SBD balance changes (but not more often than every 30 days). You should see these payments in your account history.

For vested steem (aka steem power) you do not receive interest, or at least the whitepaper doesn't call it interest. If you have steem power you will notice that the amount that you have increases over time, even if you don't earn anything in the form of author or curation rewards. What happens here is comparable to owning shares in a company. The amount of shares that you hold stays the same, but the amount of steem in the pool represented by these shares increases over time. The amount of steem in the pool increases not from someone paying interest, but from inflation. Whenever the system pays out steem as rewards, more steem is created and put into the pool. Theoretically, the inflation does not alter the total value of the system, therefore my guess would be that islam does not forbid this way of profiting.

Again, if you want to be sure consult a religious authority.