Copyright applies to all recorded works, which includes information delivered electronically via websites. The reuse of copyrighted work, regardless of the format of the original, is subject to obtaining permission from the rights-holder. This may be the author or creator, or more frequently, the publisher of the material.
When using open, online material and modules it is important to consider what material will be used. You are responsible for ensuring that you have permission for the use of any and all third party material within your online course. Gaining permission to use material can take time, so early planning is essential.
The best way to deal with copyright is to use material that is published with a Creative Commons License allowing for (non-commercial) reuse of material. For example, MOOCs are a very interesting source of useful online educational material, since it is explicitly licensed to be reused and the quality is generally high.