I'm having issues installing this too...I'm on SMF 2.0.1 using the default theme but still getting this:
11. Execute Modification ./Sources/RemoveTopic.php Test failed
1. Replace ./Sources/RemoveTopic.php Test failed
2. Add After ./Sources/RemoveTopic.php Test failed
Execute Modification ./Themes/core/Display.template.php Test failed
1. Add After ./Themes/core/Display.template.php Test failed
Maybe I'm not clear on the install. If I'm using the default theme, do I still need to go in and modify the files as shown in the manual install?