We’ve tried to keep the game as backwards-compatible as possible with mods developed for older versions. Some mods will directly work on the new version, but others may need minor changes from the developer of the mod to make them compatible with some of code/gameplay changes in the Steam version. The Steam version will also have better built-in modding tools (such as a character/animation editor and a level editor) and full Steam Workshop integration, so the release will also make it much easier to mod the game and to find and install new mods. Read more about upgrading mods here.