One again Gentoo slang-2 solution strikes.
I've got slang2 installed, but dosemu fails to detect it.
Patch files/dosemu-1.3.5-slang2.diff is broken, but is easy to fix.
Created attachment 135765 [details, diff]
Of course, as it's a patch from 1.3.5, it's affected too.
*** Bug 178399 has been marked as a duplicate of this bug. ***
Please see bug 209416
sys-libs/slang-2.1.3 and dosemu-1.4.0 fixes now