If you modified the software and then sold a hosted solution using the modified software you would need to release the source code for your modifications. Or if

If you modified the software and then sold a hosted solution using the modified software you would need to release the source code for your modifications. Or if you built a plugin that was directly linked to the software you might have to release the source for that plugin. But if you had other software that made network calls to the software I'm pretty sure you wouldn't have to open source that as well.