I bumped waimea to the 0.5.0 prerelease. It depends on x11-libs/cairo and x11-libs/libsvg-cairo which are not available in ~sparc, so I removed the keyword. If you want to support 0.5.0 please have a look at the cairo libs.
Added the ~sparc keyword to waimea-0.5.0-pre and the necessary dependencies. Thanks for teh bug :)