Nintaco is a work in progress. It is a NES-Famicom-Dendy emulator written in Java 8, ostensibly making it cross-platform. The full source will be made available per LGPLv2.1.

Getting Started
If double-clicking the jar does not automatically launch the emulator, try: java -jar Nintaco.jar
Configure input: Options | Button Mapping...
If you are using an 8 button controller, such as a USB NES gamepad, try mapping Rewind Time to Start + B.
If you want to resume at arbitrary points in the past: Tools | Watch History... and Resume Here

Nintaco (2019/03/31) changelog:

Fixed bug introduced in the last build that inhibited loading FDS and NSF files.
Fixed issue that prevented FDS games from being debugged.
Introduced ability to shoot offscreen.
Added 97 NES 2.0 mappers.
Updated the cart DB.
Updated the FAQ.