Currently GnuCOBOL uses Berkeley DB for
INDEXED SEQUENTIAL file access (essentially a persistent key-value store). However, versions after 1.85 (which is buggy) have copyleft licenses that prohibit them from being used in distributed proprietary programs.
Older simple, non-relational DBMSs exist, but data size limits make them unusable. SQLite is overkill for this, being a full SQL RDBMS.
Does anyone know of a library that would meet the needs of GnuCOBOL? If not, one probably needs to be written.