Spark uses proprietary JxBrowser component for cobrowsing/sparkmeet. They ask to add a disclaimer to the readme file:
Spark uses JxBrowser http://www.teamdev.com/jxbrowser, which is a proprietary software, owned by TeamDev Ltd. The use of JxBrowser is governed by JxBrowser Product Licence Agreement http://www.teamdev.com/jxbrowser-licence-agreement. You may not use JxBrowser separately from the Spark project without explicit permission of TeamDev Ltd.