Google's chrome team intends to remove NPAPI support completely later this year. We will keep the option available instead if they don't remove all the supporting source code from the code base. There are still a lot of people who need Java and Silverlight.
UPDATE:
We have changed the default value of this option to be ON in 4.0.4 to minimize disturbance to our users. We believe the world is not ready to live without NPAPI at this time. If you updated to earlier builds of V4 first, you still need to manually turn it on based on the instructions above. If you update from V3 or earlier directly, the NPAPI option should stay on by default.
UPDATE:
flashpeak wrote:We have started working on migrating Slimjet to Chromium 46. But we are running into some difficulty with the support of Java. We found a way to re-enable the support of NPAPI and silverlight works just fine. However, Java simply refuses to work properly so far. It looks like Google's chrome team has removed or changed a lot of the supporting code for NPAPI. We will give a few more day's work to investigate the possibility. But from what we are looking at now, we might have to live without Java in Slimjet 6 built on top of Chromium 46.
We will make Slimjet 5 available for users who have to have Java support in any case.