The Tenebrix network is weak, but still functioning. I've sent and received TBX as recently as this year.
I usually sync the blockchain with my wallet every 6 months or so, usually during computer spring cleaning time, during which I delete all the junk crypto files that accumulate. I could never bring myself to delete my TBX files, however. Altcoins come and go and are nearly all rubbish, but the original alts like TBX seem worth saving for the lulz, the nostalgia, or the history.
The Fairbrix network is a bit stronger, I've noticed, but not by much. Of the old altcoins, Liquidcoin has the most spotty network and is the only one I can't consistently sync. I was able to mine LQC until the end of last year, but the network has become extremely weak since then.
I see no reason why Tenebrix code couldn't be updated. IXCoin and I0Coin have been updated, indirectly because they have benefited from being merge mined all these years, which not only secured their networks but also kept the coins in the crypto-consciousness; whereas the non-MM coins like TBX and FBX have been relegated to mostly leftover PCs and slow CPUs. Yet it wasn't long ago that IXCoin and I0Coin seemed just as ancient as TBX.
OK, so this time I tried downloading Fairbrix from the official page here:http://github.com/coblee/Fairbrix/downloads
There are also updated versions of Fairbrix which wiggi released which incorporate some of Litecoin's features. You can find them by searching here on the forums or on Google. coblee didn't like them because he felt no need for Fairbrix to exist anymore, since Litecoin can now do everything that it does and more.
After downloading and running the official coblee client, it looks very similar to Tenebrix but unlike Tenebrix, the network is actually functional. I was able to connect to two nodes and can now download blocks. I'm currently at block 7,800. Thing's pretty fast too. I'll try mining some coins on my ancient laptop later. Shouldn't be too hard since the coin is abandoned:
UPDATE: Now I'm at 30,000 blocks. I'm not sure how long this will take. I still have only two connections though.
UPDATE 2: It's stuck at block 43,004. Not sure what's going on. I'll keep it running for a few more hours to see if it finally syncs.
UPDATE 3: Working again. 50,000th block.
UPDATE 4: 131,000 blocks downloaded. Still only two peers.
UPDATE 5: 240,000 blocks downloaded. Roughly nine hours has passed since chain began downloading.
UPDATE 6: 260,000 blocks downloaded. Since Fairbrix is roughly three years old and has a block time of 5 minutes, there should be slightly over 300,000 blocks. So it seems I'm getting close to the end.
UPDATE 7: 282,000 blocks downloaded. It's starting to get slower...
UPDATE 8: 282,671 blocks downloaded. Actually I think it's fully synced. Weird how it doesn't show it though...