The Plugin Store is where you can find plugins to download and install into your Intamerge instance. Intamerge features an open plugin architecture allowing you to expand Intamerge to have additional functionality as you wish. Anyone in the public can contribute plugins to Intamerge and have them published here for free or for commercial gain. Some plugins are published under the AGPLv2 license, but you could publish yours under a commercial license if you wish.
Read up on Plugins here