Almost all multiboxing depends on using a follow command, via the ingame interface, in order to deal with movement. Games without an ingame follow command are not good contenders for multiboxing as the slightest variation in facing, environment, lag, etc will cause the toons to veer off in different directions. Though there are exceptions {ex - Diablo 3}, games that do not provide a follow command or allow background interaction are good signs that multiboxing is not permitted.

As far as this game in particular, I have different GM posts saying multiboxing with the use of software is not allowed in the game.

http://forums.spiralknights.com/en/n...comment-216567
http://forums.spiralknights.com/en/n...comment-252613
http://forums.spiralknights.com/en/n...comment-686182
http://forums.spiralknights.com/en/n...comment-686297

you may log in multiple clients at the same time, however, you may not use software in order to control the secondary character in any way. If you want to multibox Spiral Knights, you need to do so manually by swapping between clients and operating within the TOS.