The project has received Microsoft backing as part of a controversial 2006 intellectual-property arrangement between Novell and Microsoft.
Mono, directed by Novell employee Miguel de Icaza, is aiming to create an open-source, cross-platform set of tools compatible with Microsoft's .Net programming framework.
Silverlight supports Windows and Mac OS X, and Microsoft has planned support for mobile devices, but the software does not support Linux operating systems.
Moonlight supports the Silverlight 1.0 profile for Linux, de Icaza said in a blog post Tuesday.
Users can install a downloadable version for Mozilla Firefox on Linux that does not include media codec support, or can compile the software from source code, de Icaza said. Firefox 2 and 3 are supported, he said.
The release is not yet feature-complete, and is intended for developers who want to contribute to the project, according to de Icaza. Missing features include components in media codecs and the media pipeline. The release also features about 70 known bugs, he said.
There are also some problems with recent changes to Firefox 3 that stop Moonlight from working and which require a workaround, de Icaza said.
The release supports "windowless" mode, which allows Silverlight content to blend with other HTML elements on a page, but this is supported only in Firefox 3, according to de Icaza.
The final version of Moonlight is to use audio and video codecs provided by Microsoft, as part of a wide-reaching and controversial intellectual-property deal between the software giant and Novell in late 2006.
The support of proprietary media codecs, such as those used in Silverlight, has caused some controversy within the open-source world, with Tristan Nitot, the founder of Mozilla Europe, recently warning that companies building Web sites should beware of proprietary rich-media technologies like Silverlight and Adobe's Flash.
Matthew Broersma of ZDNet UK reported from London.