when this mod is not in on server help works just fine. with this mod the help command gives java.util.NoSuchElementException.

forge-1.10.2-12.18.1.2052-universal
spongeforge-1.10.2-2052-5.0.0-BETA-1675

[10:15:29] [Server thread/INFO]: Error occurred while executing command: null
[10:15:29] [Server thread/ERROR] [Sponge]: Error occurred while executing command 'help' for source DedicatedServer: null
java.util.NoSuchElementException
at org.spongepowered.common.text.TextComponentIterator.next(TextComponentIterator.java:61) ~[TextComponentIterator.class:1.10.2-2052-5.0.0-BETA-1675]
at org.spongepowered.common.text.TextComponentIterator.next(TextComponentIterator.java:38) ~[TextComponentIterator.class:1.10.2-2052-5.0.0-BETA-1675]
at org.spongepowered.common.text.TextComponentIterator.next(TextComponentIterator.java:73) ~[TextComponentIterator.class:1.10.2-2052-5.0.0-BETA-1675]
at org.spongepowered.common.text.TextComponentIterator.next(TextComponentIterator.java:38) ~[TextComponentIterator.class:1.10.2-2052-5.0.0-BETA-1675]
at org.spongepowered.common.service.pagination.PaginationCalculator.getWidth(PaginationCalculator.java:149) ~[PaginationCalculator.class:1.10.2-2052-5.0.0-BETA-1675]
at org.spongepowered.common.service.pagination.PaginationCalculator.getLines(PaginationCalculator.java:99) ~[PaginationCalculator.class:1.10.2-2052-5.0.0-BETA-1675]
at org.spongepowered.common.service.pagination.SpongePaginationList.lambda$sendTo$0(SpongePaginationList.java:108) ~[SpongePaginationList.class:1.10.2-2052-5.0.0-BETA-1675]
at java.util.stream.ReferencePipeline$3$1.accept(Unknown Source) ~[?:1.8.0_101]
at java.util.Iterator.forEachRemaining(Unknown Source) ~[?:1.8.0_101]
at java.util.Spliterators$IteratorSpliterator.forEachRemaining(Unknown Source) ~[?:1.8.0_101]
at java.util.stream.AbstractPipeline.copyInto(Unknown Source) ~[?:1.8.0_101]
at java.util.stream.AbstractPipeline.wrapAndCopyInto(Unknown Source) ~[?:1.8.0_101]
at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(Unknown Source) ~[?:1.8.0_101]
at java.util.stream.AbstractPipeline.evaluate(Unknown Source) ~[?:1.8.0_101]
at java.util.stream.ReferencePipeline.collect(Unknown Source) ~[?:1.8.0_101]
at org.spongepowered.common.service.pagination.SpongePaginationList.sendTo(SpongePaginationList.java:110) ~[SpongePaginationList.class:1.10.2-2052-5.0.0-BETA-1675]
at org.spongepowered.common.service.pagination.SpongePaginationBuilder.sendTo(SpongePaginationBuilder.java:112) ~[SpongePaginationBuilder.class:1.10.2-2052-5.0.0-BETA-1675]
at org.spongepowered.common.command.SpongeHelpCommand.lambda$create$3(SpongeHelpCommand.java:86) ~[SpongeHelpCommand.class:1.10.2-2052-5.0.0-BETA-1675]
at org.spongepowered.api.command.spec.CommandSpec.process(CommandSpec.java:332) ~[CommandSpec.class:1.10.2-2052-5.0.0-BETA-1675]
at org.spongepowered.api.command.dispatcher.SimpleDispatcher.process(SimpleDispatcher.java:333) ~[SimpleDispatcher.class:1.10.2-2052-5.0.0-BETA-1675]
at org.spongepowered.common.command.SpongeCommandManager.process(SpongeCommandManager.java:274) [SpongeCommandManager.class:1.10.2-2052-5.0.0-BETA-1675]
at net.minecraft.command.ServerCommandManager.func_71556_a(SourceFile:82) [bd.class:?]
at net.minecraft.server.dedicated.DedicatedServer.func_71333_ah(DedicatedServer.java:423) [ld.class:?]
at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:388) [ld.class:?]
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:613) [MinecraftServer.class:?]
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:471) [MinecraftServer.class:?]
at java.lang.Thread.run(Unknown Source) [?:1.8.0_101]

without sponge i get this error running strictly forge:

[10:20:17] [Server thread/WARN]: Couldn't process command: 'help'
java.lang.IllegalArgumentException: Comparison method violates its general contract!
at java.util.ComparableTimSort.mergeLo(Unknown Source) ~[?:1.8.0_101]
at java.util.ComparableTimSort.mergeAt(Unknown Source) ~[?:1.8.0_101]
at java.util.ComparableTimSort.mergeForceCollapse(Unknown Source) ~[?:1.8.0_101]
at java.util.ComparableTimSort.sort(Unknown Source) ~[?:1.8.0_101]
at java.util.Arrays.sort(Unknown Source) ~[?:1.8.0_101]
at java.util.Arrays.sort(Unknown Source) ~[?:1.8.0_101]
at java.util.ArrayList.sort(Unknown Source) ~[?:1.8.0_101]
at java.util.Collections.sort(Unknown Source) ~[?:1.8.0_101]
at net.minecraft.command.CommandHelp.func_184900_a(SourceFile:118) ~[al.class:?]
at net.minecraft.command.CommandHelp.func_184881_a(SourceFile:73) ~[al.class:?]
at net.minecraft.command.CommandHandler.func_175786_a(CommandHandler.java:104) [k.class:?]
at net.minecraft.command.CommandHandler.func_71556_a(CommandHandler.java:83) [k.class:?]
at net.minecraft.server.dedicated.DedicatedServer.func_71333_ah(DedicatedServer.java:423) [ld.class:?]
at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:388) [ld.class:?]
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:613) [MinecraftServer.class:?]
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:471) [MinecraftServer.class:?]
at java.lang.Thread.run(Unknown Source) [?:1.8.0_101]

Not the dev, but try https://minecraft.curseforge.com/projects/helpfixer it's a server side mod that underps forge and /help commands being implemented by mods. It worked for my server, on other mods, but your mileage may vary.

help fixer did not resolve. IoP from ftb irc room already suggested that. But thanks for the tip.

A couple of commits have been pushed to SpongeCommon to fix this, latest commit is SpongePowered/Sponge@310edef...85d7913

Strange, I don't even touch the /help command, I just have a /config /coroutil and /coroutilc for client side

Edit: Ah, I bet that method for sponge probes mod commands to output help on them and theres some spec I don't have implemented, anyone know of a reference for that?

According to the guys over at #spongedev it is a bug in sponge itself, leaving it with them as they are looking into it, will keep this ticket open for a bit.