sys-libs/openipmi is a tad stale. The current "Stable" release is 1.4.27 (for the 1.x series) 2.0.7 (for the 2.0 series) Renaming the current ebuild to openipmi-2.0.7.ebuild seems to be all that is required to build 2.0.7. (Assuming the source tarball is fetchable).
There's now a 2.0.11 ebuild; copying the 1.4.14 ebuild to 2.0.11 "just worked" (on amd64 architecture).
in cvs.