Is it legit to create mod?

Is it permitted to create mods for any of Beamdog games? According to EULA, which is available at https://www.beamdog.com/about/EULA, the next is stated:

> "Software" includes the Beamdog Player and other software purchased in the store. "Software" further includes executable computer programs and any related printed, electronic and online documentation and any other files that may accompany the product.
> The Software may not be modified, reverse-engineered, or de-compiled in any manner through current or future available technologies.
> Failure to comply with any of the terms under the License section will be considered a material breach of this Agreement.

So therefore I can only make conclusion that it is forbidden by holder of copyright to do any modding activity. However, here we have big modding forum with lot of mods, including some exclusively for BG:EE. How can this be? What are really limitations of modding activity? Can I make mod and sell it as standalone product?