1. What technically separates Bytecoin and Monero? Aren't they both using CryptoNote?
Bytecoin was first, but it was mined two years in secret with the same machines (no underground massive discovery, difficulty from block 5,000 to 400,000 are about the same)
Monero is the first CryptoNote that had a fair launch.
2. Why did Bytecoin die out and what will prevent Monero from doing the same?
It hasn't died out.
The CryptoNote technology has a lot of potential and apart from the Bytecoin premine, Monero is first.
So Monero has the first mover advantage. If you're interested in CryptoNote technology it might be wise to invest in all the CryptoNote coins.
3. Monero offers anonymity, but so does DarkCoin. Why would anyone choose Monero when DK has a larger community?
Ring signatures technology inside CryptoNote (Monero) offers true decentralised anonymous transactions.
Please read the whitepaper here:
https://cryptonote.org/whitepaper.pdfAlso the creator of CoinJoin that Darkcoin is based off of (gmaxwell), who is also a core bitcoin developer said that CryptoNote technology works and blows CoinJoin out of the water.
4. When will Monero get a GUI wallet (which anyone can install...) ?
At least one member of this community is working on a GUI for anyone to install. Like Bitcoin GUI.
Remember this technology is very new, this isn't a bitcoin source code copy pasta job.
We have lots of issues, transaction size, wallets working easily for services (exchanges) etc... this is early days for this technology.
Please read the whitepaper.
EDIT: regarding Darkcoin, remember a Masternode can record all the transactions it joins.
Evan is working on the next version that will make your transactions route through 10 or so Masternodes to achieve anonymity from node owners, potentially causing worse blockchain bloat than Monero. This is still flawed because Masternodes can be attacked and the effect is to force your transaction through to bad recording nodes.