"Lossless" means that the output from the decompressor is bit-for-bit identical with the original input to the compressor. Lossless only occurs when the compression color space matches the input and output color space. When the color spaces do not match, a low loss compression is performed.
The original implementation was written for Windows by Ben Rudiak-Gould and published under the terms of the GPL. The Huffyuv 1.1 was released in 2000. The implementation is considered very fast, giving a compression throughput of up to 38 megabytes per second on a 416 MHz Celeron. The official Huffyuv has not had a new release since 2002.
Huffyuv 2.1.1 with CCESP patch 0.2.5 was released to address problems particularly for compatibility with Cinema Craft Encoder.
Huffyuv MT is a multi-threaded version that uses a different FourCC.
The FFmpeg project also contains an implementation of HuffYUV which allows HuffYUV files to be created & played on Linux and Mac OS X. Additionally, this means that many of the applications which use FFmpeg as a base can also play/create HuffYUV files, including VLC media player, MPlayer and ffdshow.