Looked into it more, indeed the process that the launchd job wants to launch is not actually running. So I tried invoking it manually and got an immediate crash-on-launch:
cbackas@Radiant-Dawn ~> sudo /Applications/PlasticSCMServer.app/Contents/MacOS/plasticd --daemon
Process terminated. Infinite recursion during resource lookup within System.Private.CoreLib. This may be a bug in System.Private.CoreLib, or potentially in certain extensibility points such as assembly resolve events or CultureInfo names. Resource name: Arg_AccessViolationException
at System.Environment.FailFast(System.String)
at System.SR.InternalGetResourceString(System.String)
at System.SR.GetResourceString(System.String, System.String)
at System.AccessViolationException..ctor()
at System.Reflection.CustomAttribute.FilterCustomAttributeRecord(System.Reflection.MetadataToken, System.Reflection.MetadataImport ByRef, System.Reflection.RuntimeModule, System.Reflection.MetadataToken, System.RuntimeType, Boolean, ListBuilder`1<System.Object> ByRef, System.RuntimeType ByRef, System.IRuntimeMethodInfo ByRef, Boolean ByRef, Boolean ByRef)
at System.Reflection.CustomAttribute.AddCustomAttributes(ListBuilder`1<System.Object> ByRef, System.Reflection.RuntimeModule, Int32, System.RuntimeType, Boolean, ListBuilder`1<System.Object>)
at System.Reflection.CustomAttribute.GetCustomAttributes(System.Reflection.RuntimeModule, Int32, Int32, System.RuntimeType)
at System.Reflection.CustomAttribute.GetCustomAttributes(System.Reflection.RuntimeAssembly, System.RuntimeType)
at System.Reflection.RuntimeAssembly.GetCustomAttributes(System.Type, Boolean)
at System.Attribute.GetCustomAttributes(System.Reflection.Assembly, System.Type, Boolean)
at System.Attribute.GetCustomAttribute(System.Reflection.Assembly, System.Type, Boolean)
at System.Reflection.CustomAttributeExtensions.GetCustomAttribute[[System.__Canon, System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]](System.Reflection.Assembly)
at System.Resources.ManifestBasedResourceGroveler.GetNeutralResourcesLanguage(System.Reflection.Assembly, System.Resources.UltimateResourceFallbackLocation ByRef)
at System.Resources.ResourceManager.CommonAssemblyInit()
at System.Resources.ResourceManager..ctor(System.Type)
at System.SR.get_ResourceManager()
at System.SR.InternalGetResourceString(System.String)
at System.SR.GetResourceString(System.String, System.String)
at System.AccessViolationException..ctor()
at System.Collections.Generic.Dictionary`2[[System.__Canon, System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[System.__Canon, System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].TryGetValue(System.__Canon, System.__Canon ByRef)
at System.AppContext.GetData(System.String)
at System.Runtime.InteropServices.RuntimeInformation.get_FrameworkDescription()
at log4net.Core.LoggerManager.GetVersionInfo()
at log4net.Core.LoggerManager..cctor()
at log4net.Core.LoggerManager.CreateRepository(System.String)
at log4net.LogManager.CreateRepository(System.String)
at afe..cctor()
at afe..ctor(System.String)
at afd.a(System.String)
at am5..cctor()
at agm.a(System.String[])
Hope that helps!