The Western Libertarian Alliance is a very informal coalition of libertarian activists that has grown primarily out of the old Arizona Libertarian Party. Its website is http://www.WestLibAlliance.org, and you can learn more about the organization there. The original idea came from noted author L. Neil Smith, I believe. Unsurprisingly, the WLA tends to adopt the philosophical positions for which he and other radical libertarians such as Vin Suprynowicz and Rick Tompkins are noted.
One important thing to understand is that "Western" doesn't really have a geographical connotation, even though it happens to be where the movement was born. Think of it as a free state of mind.
I think of it as West of Today, and the Trail to Tomorrow.
Hence the caption at the bottom of the design, "Blazing the Trail to Tomorrow".
Because of the informal nature of the WLA, this design, products using it, and websites featuring it aren't "official." Members just pursue the goals of the WLA in their own way -- usually with plenty of input from others. Those who like this logo will be the people ordering these products, which are priced at the cost of our supplier, CafePress.com.
Want to see this design on shirts and mugs and stuff? You can go right to the LibertariAntics Store's WLA Department!