There is an outstanding issue with Grails on certain environments (see: http://jira.codehaus.org/browse/GRAILS-4295) where parameters are not parsed correctly. The work around is to surround the parameter in double quotes so for example:

grails maven-deploy "--repository=snapshot"

The problem lies in that you can't escape the inner quotes in the Target field when building a Hudson project so:

"grails maven-deploy \"--repository=snapshot\""

Throws the following error when the project is next built:
org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed, Script1.groovy: 1: expecting EOF, found 'repository' @ line 1, column 12.
1 error

at org.codehaus.groovy.control.ErrorCollector.failIfErrors(ErrorCollector.java:296)
at org.codehaus.groovy.control.ErrorCollector.addFatalError(ErrorCollector.java:143)
at org.codehaus.groovy.control.ErrorCollector.addError(ErrorCollector.java:113)
at org.codehaus.groovy.control.ErrorCollector.addError(ErrorCollector.java:125)
at org.codehaus.groovy.control.SourceUnit.addError(SourceUnit.java:353)
at org.codehaus.groovy.antlr.AntlrParserPlugin.transformCSTIntoAST(AntlrParserPlugin.java:92)
at org.codehaus.groovy.antlr.AntlrParserPlugin.parseCST(AntlrParserPlugin.java:59)
at org.codehaus.groovy.control.SourceUnit.parse(SourceUnit.java:249)
at org.codehaus.groovy.control.CompilationUnit$1.call(CompilationUnit.java:160)
at org.codehaus.groovy.control.CompilationUnit.applyToSourceUnits(CompilationUnit.java:801)
at org.codehaus.groovy.control.CompilationUnit.compile(CompilationUnit.java:466)
at groovy.lang.GroovyClassLoader.parseClass(GroovyClassLoader.java:281)
at groovy.lang.GroovyShell.parseClass(GroovyShell.java:590)
at groovy.lang.GroovyShell.parse(GroovyShell.java:602)
at groovy.lang.GroovyShell.parse(GroovyShell.java:582)
at groovy.lang.GroovyShell.evaluate(GroovyShell.java:560)
at groovy.lang.GroovyShell.evaluate(GroovyShell.java:536)
at com.g2one.hudson.grails.GrailsBuilder.evalTarget(GrailsBuilder.java:212)
at com.g2one.hudson.grails.GrailsBuilder.perform(GrailsBuilder.java:168)
at hudson.tasks.BuildStepMonitor$1.perform(BuildStepMonitor.java:19)
at hudson.model.AbstractBuild$AbstractRunner.perform(AbstractBuild.java:600)
at hudson.model.Build$RunnerImpl.build(Build.java:174)
at hudson.model.Build$RunnerImpl.doRun(Build.java:138)
at hudson.model.AbstractBuild$AbstractRunner.run(AbstractBuild.java:416)
at hudson.model.Run.run(Run.java:1244)
at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:46)
at hudson.model.ResourceController.execute(ResourceController.java:88)
at hudson.model.Executor.run(Executor.java:122)