Spices.Net license is machine based license (per machine),
yes, single license is enough.
As I've understood you plan to use MSBuild integration.
In this case you need to purchase Spices.Obfuscator license, as Spices.Obfuscator console package doesn't including MSBuild integration.
Spices.Obfuscator package include MSBuild and console version of Spices.Obfuscator.