The free version of SpiderBasic (limited to small webapps) is available for download for everyone:

Registering SpiderBasic gives you access to full-sized webapps, the three versions of SpiderBasic (Linux, Windows and OS X) will be immediately available on your online account. There is also an exclusive access for registered users to forthcoming beta version if you want to test it before official release.

For more info about pricing, see the pricing section.