Hola and welcome to the forum. The first rule of forums is to search before posting.
If you search the forum you will see the forum admin and the moderators have explained in a number of threads why the source code is not yet available. See for example
this post.
Just to bring you up to date: Lightworks is currently a Windows application. Before the source code can be released, it has to be prepared, technically and legally, and this is a long process. Also, during this time, the code is being worked on to improve the ability of Lightworks to work on a very wide range of hardware, as, before the Beta program, it was only supplied as a turnkey system on a very specific set of hardware.
I would add that Lightworks is 20 year old Windows software owned by different companies during this time. Its current owners, EditShare, decided to make it open source only last year. Before then, Lightworks was only available with purpose built hardware as a complete "turn key" solution.
The developers are now in the process of Beta testing it on a multiplicity of hardware combinations that exist on forum members PCs. And the code is being prepared technically and legally for open source release (scheduled for Summer 2011). Hundreds of thousands of pages of 20 year old code are being inspected for intellectual property licensing issues. You should know that free software is a legal minefield and the code must be free from such issues before it can be released.
The development of a Linux and Mac version of Lightworks is scheduled for quarters 3 and 4 of 2011. See the
Lightworks roadmap.