Q. Can shaders created with Eilir be distributed commercially?
A. Yes and no. The .elr files are completely distributable free or commercially. All the generated scripts are as well.
However, the actual RSL shaders as a whole are another manner, and its a node by node basis. This is because many of the nodes are based on code that is found in standard Renderman Books and on sights like renderman.org. Anything from renderman.org you need to observe the renderman.org policy (this includes all the "arman" nodes).
Nodes by you, (or ones found in the Eilir folder under nodes, and any under shaderops)) are of course fully distributable.
One way you can distribute to get around this problem, though, is to included everything but the actual RSL shaders. Then have your user open Eilir on one of the surfaces using the created material and have them press apply/generate which will generate the material locally.