If the artist grants the right to sub-license, the artist can demand a percentage of the fee received for sublicensing. The qu estion of licensing artwork to a third-party is complicated. Briefly, however, we recommend that the right to license artwork to a third party NOT be included in a contract unless the basic elements of the third-party license are spelled out. In general, when a third party acquires rights to use artwork, the third party should be under the same copyright limitations as any other client, and the artist should receive the same fees as with any other client. For instance, most contracts with agents have termination clauses, which govern the basis on which the parties can dissolve the relationship, and how long after dissolution the agent can either rep the artist or receive payment for jobs the agent has gotten the artist.
Duties are generally specific to the contracting parties, but assignments can be transferred.
We'll discuss this in terms of illustration. If the illustrator cannot perform his duties and contracted, the deal is off. In exchange for doing the drawing, the illustrator has the right to get paid. The client has the duty to pay, and for fulfilling that duty gains certain rights to the work. If the client wishes to assign its rights in the art to a third party, that may be permissible, as long as the contract clearly states that the rights assigned are no greater than those the client would have had.