Version 7_0 is available upstream. Please consider updating! It seems that version 7_0 is available upstream, while the latest version in the Gentoo tree is 2.6.1. You think this warning is false? Read more about it here.
mt32emu_alsadrv is a module of the Munt project. It uses the mt32emu library and provides an ALSA MIDI driver which emulates (approximately) the Roland MT-32, CM-32L and LAPC-I synthesiser modules.