The artifact of the project currently published on Maven Central is broken and can't be checked out automatically with dependency management systems. The Jar file can, however, be manually downloaded.

The POM of the artifact org.fnlp.fnlp-core contains the following parent tag:

However, there is no artifact called fnlp-all in Maven Central.
It is therefore not possible to use it as a managed dependency; the download will fail.

Solution

I believe the simplest solution would be to re-publish the artifact removing the tag altogether.

Effect

When using the following snippet with Leiningen:

[org.fnlp/fnlp-core "2.1"]

and running lein deps, the build fails with the following message:

Retrieving org/fnlp/fnlp-core/2.1/fnlp-core-2.1.pom from central
Retrieving org/fnlp/fnlp-core/2.1/fnlp-core-2.1.jar from central
Could not find artifact org.fnlp:fnlp-all:pom:2.1-SNAPSHOT in clojars (https://repo.clojars.org/)

A workaround is to download the jar manually; however, this makes production deployment impossible in my environment.