AFAIK the original Duelyst team gave the Duelyst 2 team some code (long before open-sourcing), but they added some new features and a lot of polish, most notably reintroducing 2-card draw. But Duelyst 2 is monetized with lootboxes (free to download), and right now pay-to-win as it otherwise takes a ton of grinding to unbox or craft the right epic and legendary cards.
It’s really interesting. They’re monetizing a game which is mostly open-source: if you don’t agree with it you can play an almost-the same game, and it seems like a separate small could make it even closer to the same with a few months of work. But (reading on the r/Duelyst forms), it seems to be working: some people have already spent thousands on the new game.
As much as I hate IAP, I am kind of glad for the Duelyst 2 devs because they did put a lot of effort into fixing up the game. It would be a shame if this small team worked so hard and still accomplished nothing because everything they worked on is already public. But moreover, it goes to shows why so many companies (even "good" ones) implement IAP that lets people spend absurd amounts of money. Because it's ethically dubious, but it works, some people do, and you can argue that the extra $1000 lets you make up for it in more gameplay content. One "compromise" is to put most of the monetization on cosmetics which don't affect gameplay and unnecessary boosts, while keeping the F2P progression system fast and game skill-based. It seems LoR has done this, and Duelyst 2 has originally indicated they were going to do this although they have not, the last patch scaled back some of the F2P grinding and I wouldn't be surprised if they scale it back further after the revenue starts dropping to restore popularity and mitigate criticism (I doubt increasing the monetization after revenue starts dropping will help, so how else to bring it back up...)
And note that open Duelyst has been around for a couple months now (around when Duelyst 2 was released), and Duelyst’s community is niche and the openness has been discussed frequently, so I doubt most people didn’t realize. There’s also https://duelyst.gg which existed much longer than Duelyst 2 and has everything unlocked by default: it’s more similar to open Duelyst, an online version re-engineered from the assets and some of the code before the rest was made available.