As there is no prebuild release, I've tried to build it myself.
It fails, as the path for 1.14 is wrong it seems (I tried to build for every version as I have no clue how to build for 1.15.x paper ^^)
[INFO] ------------------< com.lishid:openinvadapter1_14_R1 >------------------ [INFO] Building OpenInvAdapter1_14_R1 4.0.9-SNAPSHOT [6/8] [INFO] --------------------------------[ jar ]--------------------------------- Downloading from spigot-repo: https://hub.spigotmc.org/nexus/content/groups/public/org/spigotmc/spigot/1.14.3-R0.1-SNAPSHOT/maven-metadata.xml Downloading from spigot-repo: https://hub.spigotmc.org/nexus/content/groups/public/org/spigotmc/spigot/1.14.3-R0.1-SNAPSHOT/spigot-1.14.3-R0.1-SNAPSHOT.pom [WARNING] The POM for org.spigotmc:spigot:jar:1.14.3-R0.1-SNAPSHOT is missing, no dependency information available Downloading from spigot-repo: https://hub.spigotmc.org/nexus/content/groups/public/org/spigotmc/spigot/1.14.3-R0.1-SNAPSHOT/spigot-1.14.3-R0.1-SNAPSHOT.jar [INFO] ------------------------------------------------------------------------ [INFO] Reactor Summary for OpenInvParent 4.0.9-SNAPSHOT: [INFO] [INFO] OpenInvParent ...................................... SUCCESS [ 8.019 s] [INFO] OpenInvAPI ......................................... SUCCESS [ 13.550 s] [INFO] OpenInvPlugin ...................................... SUCCESS [ 3.662 s] [INFO] OpenInvInternal .................................... SUCCESS [ 0.027 s] [INFO] OpenInvAdapter1_8_R3 ............................... SUCCESS [ 4.176 s] [INFO] OpenInvAdapter1_14_R1 .............................. FAILURE [ 5.468 s] [INFO] OpenInvAdapter1_15_R1 .............................. SKIPPED [INFO] OpenInvAssembly .................................... SKIPPED [INFO] ------------------------------------------------------------------------ [INFO] BUILD FAILURE [INFO] ------------------------------------------------------------------------ [INFO] Total time: 35.083 s [INFO] Finished at: 2020-04-10T22:06:00+02:00 [INFO] ------------------------------------------------------------------------ [ERROR] Failed to execute goal on project openinvadapter1_14_R1: Could not resolve dependencies for project com.lishid:openinvadapter1_14_R1:jar:4.0.9-SNAPSHOT: Could not find artifact org.spigotmc:spigot:jar:1.14.3-R0.1-SNAPSHOT in spigot-repo (https://hub.spigotmc.org/nexus/content/groups/public/) -> [Help 1]
What Robo said. The readme also details manual installation here in case you are using pre-BuildTools artifacts.
As far as releases go, I believe I had a couple more things I wanted to get done before pushing a build, as this will end up being a minor version bump.
As there is no prebuild release, I've tried to build it myself. It fails, as the path for 1.14 is wrong it seems (I tried to build for every version as I have no clue how to build for 1.15.x paper ^^)
[INFO] ------------------< com.lishid:openinvadapter1_14_R1 >------------------ [INFO] Building OpenInvAdapter1_14_R1 4.0.9-SNAPSHOT [6/8] [INFO] --------------------------------[ jar ]--------------------------------- Downloading from spigot-repo: https://hub.spigotmc.org/nexus/content/groups/public/org/spigotmc/spigot/1.14.3-R0.1-SNAPSHOT/maven-metadata.xml Downloading from spigot-repo: https://hub.spigotmc.org/nexus/content/groups/public/org/spigotmc/spigot/1.14.3-R0.1-SNAPSHOT/spigot-1.14.3-R0.1-SNAPSHOT.pom [WARNING] The POM for org.spigotmc:spigot:jar:1.14.3-R0.1-SNAPSHOT is missing, no dependency information available Downloading from spigot-repo: https://hub.spigotmc.org/nexus/content/groups/public/org/spigotmc/spigot/1.14.3-R0.1-SNAPSHOT/spigot-1.14.3-R0.1-SNAPSHOT.jar [INFO] ------------------------------------------------------------------------ [INFO] Reactor Summary for OpenInvParent 4.0.9-SNAPSHOT: [INFO] [INFO] OpenInvParent ...................................... SUCCESS [ 8.019 s] [INFO] OpenInvAPI ......................................... SUCCESS [ 13.550 s] [INFO] OpenInvPlugin ...................................... SUCCESS [ 3.662 s] [INFO] OpenInvInternal .................................... SUCCESS [ 0.027 s] [INFO] OpenInvAdapter1_8_R3 ............................... SUCCESS [ 4.176 s] [INFO] OpenInvAdapter1_14_R1 .............................. FAILURE [ 5.468 s] [INFO] OpenInvAdapter1_15_R1 .............................. SKIPPED [INFO] OpenInvAssembly .................................... SKIPPED [INFO] ------------------------------------------------------------------------ [INFO] BUILD FAILURE [INFO] ------------------------------------------------------------------------ [INFO] Total time: 35.083 s [INFO] Finished at: 2020-04-10T22:06:00+02:00 [INFO] ------------------------------------------------------------------------ [ERROR] Failed to execute goal on project openinvadapter1_14_R1: Could not resolve dependencies for project com.lishid:openinvadapter1_14_R1:jar:4.0.9-SNAPSHOT: Could not find artifact org.spigotmc:spigot:jar:1.14.3-R0.1-SNAPSHOT in spigot-repo (https://hub.spigotmc.org/nexus/content/groups/public/) -> [Help 1]