/home/adam/sources/ktorrent/plasma/dataengine/engine.cpp: In constructor ‘ktplasma::Engine::Engine(QObject*, const QVariantList&)’:
/home/adam/sources/ktorrent/plasma/dataengine/engine.cpp:32: error: no matching function for call to ‘Plasma::DataEngine::DataEngine(QObject*&, const QList<QVariant>&)’
/usr/lib/kde4/include/plasma/dataengine.h:69: note: candidates are: Plasma::DataEngine::DataEngine(QObject*)
/usr/lib/kde4/include/plasma/dataengine.h:52: note: Plasma::DataEngine::DataEngine(const Plasma::DataEngine&)
/home/adam/sources/ktorrent/plasma/dataengine/engine.cpp: In member function ‘void ktplasma::Engine::dbusServiceUnregistered(const QString&)’:
/home/adam/sources/ktorrent/plasma/dataengine/engine.cpp:90: error: ‘removeAllData’ was not declared in this scope
/home/adam/sources/ktorrent/plasma/dataengine/engine.cpp: In member function ‘void ktplasma::Engine::removeTorrent(const QString&)’:
/home/adam/sources/ktorrent/plasma/dataengine/engine.cpp:106: error: ‘removeAllData’ was not declared in this scope

Is this an issue with my libplasma version or a bug with ktorrent? Also, I didn't see a way to not build this part of ktorrent with a cmake flag, is there one?

Install KDE 4.1beta2 or a later svn version, it should compile with that release