Unfortunately, no. Although the standalone version of VoiceAttack (available from VoiceAttack.com) and the Steam version are functionally identical, they are each bound by different licensing/DRM. The Steam version depends on the Steam client, and the standalone version depends on a registration key.
If the reason that you would need both versions happens to be that you are wanting to run VoiceAttack without the Steam client, you can actually do this with the Steam version. After you've installed VoiceAttack from the Steam client and run VoiceAttack just once (VoiceAttack pairs itself with your PC the first time you run it), you just need to launch VoiceAttack from its installed location (usually C:\Program Files (x86)\Steam\steamapps\common\VoiceAttack).
Hope that helps!