There is Shinobi & Samurai (free), an OD&D clone. It has classes like Bushi and Shinobi.
Scarlet Heroes (free quickstart, affiliate links), one of my favorites from grandmaster Kevin Crawford (Sine Nomine Publishing). The setting is called Red Tide. It's Asian flavored but also post-apocalyptic/horror. Strictly speaking no samurais and katanas.
Ruins & Ronin (affiliate link) is based on Swords & Wizardry WhiteBox. Here is a review from Sword And Board.
While writing this article, I also found Flying Swordsmen (free). Wuxia/Imperial China and cinematic rather than feudal Japan. It has a stunt system. It is a retro-clone of Dragon Fist. WoTC sold Dragon Fist to Green Ronin but they didn't do anything with it. Legally, it's in the nimbus but you can still find it on Scribd. Rules-wise Dragon Fist was close to AD&D 2nd edition.
Here is a review of Flying Swordsmen.
What's missing in this list of D&D-style-retroclones?
Yep, it's a The Black Hack hack.
Every other day there is a new product for this rules-lite old school game. We have Cyberpunk, sci-fi, Victorian, Tékumel and more.
Kaigaku is an ambitious project but not an unreasonable one. The author, Jacob DC Ross, has already drafted a free beta version. The release version will have expanded content (more clans etc.) and artwork.
The stretch goals are well thought out. The creator posts updates with the new content, so you'll get a sense of the material.
He also has read Kevin Crawford's articles on crowdfunding. That's a plus. Kevin knows how to fulfill a project and has written some good guidelines.
Will The Black Hack be a good fit for a Samurai game? That's what I'm interested in. We'll see.
Brendan Davis from Bedrock Games (the guys behind Wandering Heroes of Ogre Gate) has posted an interesting interview with Jacob Ross on his site.
Check it out if you're interested.
The core PDF is USD $10 ($15 with stretch goals). The printed book coupon is $20 ($25 with stretch goals). Distribution via Onebookshelf, that means you'll have to pay shipping and printing costs separately.
Deadline: Oct 2nd, 2016.