First on the link, that's good, thanks. They are calling it fungus, not algae as I suspected. But I do not agree with their assumption that it is harmless. I know from personal experience that some fungi from Mopani wood is toxic. I added one smallish branch of Mopani to my 90g and within 2 days this "fungus" appeared; simultaneously, I had cloudy water that clearly stressed the corys in particular they were respirating very fast and became agitated, until I pulled the wood out and changed 75% of the tank. After scrubbing and boiling the wood, I put it in a tank of water (no fish) for 3 months; no fungus, so I put it in my 33g with fish; it seemed fine for a few weeks, then suddenly fish were dying and I discovered a patch of fungus again, so i tossed the wood. We had a coupe other threads a while back on Mopani wood fungus, and Dawn [bettababy] who is highly versed in this, more than I am, noted that some types of fungus are deadly and the wood should be discarded rather than risk the fish.
To your photo, I agree this does not look quite the same, but I also agree with bearwithfish that the wood in the photo looks bad, as does the water. I would get rid of this wood. It is just not worth risking fish (eventually).
We don't know where this wood comes from, by which i mean, we can't be sure what it may have been exposed to at some point during its life. Years ago I started losing fish in my 115g, and tested for everything imaginable without success. Then a biologist suggested I remove the wood and do a major water change; end of problem. It took a total tear-down of the tank to remove the "toxin" that had leeched out from a huge chunk of reddish wood and obviously collected everywhere--gravel, plants, filter media. But the problem was gone with the wood.