Who publishes artefacts with groupId "com.force.api" to mvnrepository.com?

I suspect they are originating from the WSC - Force.com Web Service Connector (formerly https://github.com/forcedotcom/wsc). I'm basing this off com.force.api : force-partner-api : 38.0.0 and Issue com.force.api:force-partner-api: wrong default auth endpoint since 34.0.0

Additionally, files like force-metadata-api-38.0.0.pom also reference back to https://github.com/forcedotcom/java-sdk.
The Salesforce WSC consumes the various SOAP APIs and generates the required Java integration code.
From sfdc-wsc-maven:
Fork from sfdc-wsc v22.0 which project structure has been converted to a Maven one.
Do not confuse it with the other Maven port force-wsc which is also a fork from sfdc-wsc v22.0 and which source repository is located on GitHub.
So I think the mvnrepository you referenced in the question is the "other Maven port" referenced above.