hledger is a famous text-based accounting package. It is written in Haskell, and it runs on various Linux and BSDs.
For this project, you need to (1) get it to compile on OpenBSD, which shouldn't be too difficult, (2) create a ports entry (i.e. something that goes into /usr/ports) and (3) compile it for amd64 as a package that can be installed with pkg_add.
I'll pay a premium if you can get it included in the official OpenBSD ports tree (say whether you can do this in your response).